UPPER MARLBORO, Md. -- During roll call Wednesday, Prince George's County Public Safety Director Vernon Herron told corrections center guards that if they don't cooperate with the homicide investigation at the jail, they could be fired, News4 has learned.

"Each of you may exercise the full range of your Constitutional rights and to confer with legal counsel, as well as having an attorney present during the interview," Herron wrote in a letter to corrections employees later Wednesday. "This also includes exercising your Fifth Amendment right against self-incrimination. Failure of any individual to make themselves available to investigators will result in the county taking whatever appropriate actions are available under the law."

The investigation was launched after Ronnie White, 19, was found slain in his Prince George's County jail cell a day after he was arrested in the killing of Cpl. Richard Findley, 39. White had been charged with first-degree murder. Police said White was the driver of a pickup truck that struck Findley on Friday.

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The investigation into White's death was put into something of a holding pattern on Tuesday because many of the corrections officers the FBI and Maryland State Police want to question are in the process of obtaining legal counsel, officials said. Sources told News4 that the corrections officer union told the guards not to talk to investigators.

"I know there are some who have had reservations, but again, we are trying to find ways to work through that so we can get statements from everybody who's got information," Prince George's County State's Attorney Glenn Ivey said.

On Tuesday, Bobby G. Henry Jr., the attorney representing the inmate's family, called for "a thorough and exhaustive investigation." The family is "absolutely, unequivocally outraged and incensed and deeply saddened for the loss of life of their loved one," he said.

Henry opened by saying, "The family of Ronnie L. White, wishes to extend, first and foremost, their deepest sympathy to the family of Officer Richard Findley."

Henry later angrily denounced the actions that led to White's death, saying "a yet-to-be-identified person or persons took it upon themselves to be both the judge, the jury and the executioner."

White's death is being investigated as a homicide by the FBI and Maryland State Police. The state medical examiner said White died from asphyxiation and strangulation. He suffered two broken neck bones.

Sources told News4 that more than two dozen corrections officers could have had access to White. Officials said seven guards had access at the time of White's death, as did an unspecified number of supervisors. Authorities also are investigating whether anyone from the outside had access to White.

State police are leading the probe at the request of county officials. The FBI is focusing on possible civil rights violations. The jail also is conducting an internal investigation.

"We are going to do everything within our powers to assure that justice is served," said Prince George's County Executive Jack Johnson. "We are going to work hand in hand with the FBI and Maryland State Police to ensure that those who are involved to be brought to justice.

"If we have vigilante justice, our society will fall apart. If we tolerate these kinds of acts, then the courts are superfluous," Johnson said.

Johnson said that he believes the death was "unrelated to any act by the Prince George's County Police Department."

Ivey said Wednesday that the investigation was moving slow. Investigators still were at the jail on Wednesday interviewing inmates. Log records are being checked, and White's cell has been processed for forensic evidence.

"If the Department of Corrections is going to take administrative action and suspensions, that's up to them, but before I take any steps, I've got to make sure that I've got evidence to prove a case, and we have to prove it beyond a reasonable doubt," Ivey said.

Curtis Knowles, president of the Prince George's County Correctional Officers Association, defended the jail's employees.

"It's going to be hard for me to believe that any one of my employees, my members, had it in their hearts to do harm to Mr. White," Knowles said.

The Prince George's County chapter of the National Association for the Advancement of Colored People called for a full investigation into the practices at the jail.

"He stayed in the custody of the Department of Corrections way too long," said June White-Dillard of the Prince George's County NAACP. "He should have been transferred immediately. Obviously, his civil rights have been violated."

White-Dillard said that she was pleased the FBI was investigating the case but disturbed by the nature of the death of the inmate.

"No one should have had access to him that could have caused him harm," she said.

Henry said White did not see an attorney while he was at the jail.

"The County Council will not speculate on the events that transpired and will rely on the facts that are gleaned from the investigation by the State Police and the Federal Bureau of Investigation," said Prince George's County Council Chair Samuel Dean in a statement released Tuesday. "We must allow the justice process to work in this situation and halt any further influences to hinder it.

"We will not tolerate violence on our streets or in our facilities. Public safety and the well-being of all Prince George's County residents is a priority for this Council."

White was found alone sitting on the floor of his cell -- leaning against the bed -- at the Prince George's County jail at 10:30 a.m. Sunday with no pulse, according to officials. Jail medical staff who treated him reported no visible signs of trauma on his body.

White was admitted to the jail at 12:24 a.m. Saturday and given a medical assessment before being placed in a cell. Henry said White's family learned of his arrest through the media on Saturday.

Jail officials said he had been classified as a "high-profile offender" and was being housed alone in a maximum-security cell with steel doors. Guards checked on him every 30 minutes. He was on 23-hour lockdown, and his movement in and out of the cell was logged.

Guards checked on White about 10:15 a.m. Sunday. At the time, he was sitting on the edge of his bunk and appeared alert, according to a press release.

When they returned at 10:30 a.m. with his lunch, corrections officers found White "sitting on the floor" of his jail cell, unresponsive, the release said.

Guards could not revive him or detect a pulse. An ambulance took him to the Prince George's County Hospital Center at 11:08 a.m. He was admitted at about 11:28 a.m. and pronounced dead at 11:39 a.m., the release said.

Henry said the family also was upset by the delay in notification. He said it wasn't until about 2 p.m. that the jail's chaplain notified White's family and told them to go to Prince George's County Hospital Center. When they arrived at the hospital, they learned White's body was no longer at there but in the possession of the medical examiner's office in Baltimore.

"At this very moment, the family has not even seen the body of their loved one," Henry said. "Something is wrong. They have been denied the opportunity to start the grieving process, which naturally must occur."

Knowles said he was working that day but not in the unit. Officers involved in monitoring the inmate told Knowles that they went to feed White, tapped on the window and yelled through a slot in the door, but White didn't reply. They went in and shook White, but he didn't respond, Knowles said.

Herron said White was in a solitary cell at the jail and that he was separated from other inmates in the facility. Herron said no video cameras were in the area where White was being held.

White was one of four people taken into custody Friday after Findley, a veteran police officer, was struck and killed by the driver of a stolen pickup truck.

Findley had been monitoring the truck on Laurel-Bowie Road when at least two men returned to the vehicle, police said. Findley attempted to block the truck during an attempted traffic stop, which is when he was struck and dragged by the truck, according to charging documents.

Findley fired upon the truck, striking one of the people inside, according to court documents. That man identified White as the driver.

According to court records, White pleaded guilty to illegal possession of a firearm last year and to drug possession in another case. In 2006, he was charged with first-degree assault and armed robbery, but the case was dropped, records show. Last November, he was sentenced to more than six months in prison, but it's not clear when he was released.

It was unclear if White had an attorney, and family members could not be immediately located.

Prince George's County Police Chief Melvin High said the other three people who were taken into custody have been released.

A funeral service for Findley is set for 11 a.m. Thursday at St. Joseph's Church in Beltsville with interment at Lakemount Memorial Gardens in Davidsonville. Viewings were held from 2 p.m. to 4 p.m. and 7 p.m. to 9 p.m. on Wednesday at Borgwardt Funeral Home in Beltsville.

Gov. Martin O'Malley has ordered the Maryland flag be lowered in memory of Findley, a 10-year veteran of the Prince George's County Police Department and a volunteer with the Beltsville Volunteer Fire Department.

The state flag is to be flown at half-staff until sunset Thursday.

Stay with News4 and nbc4.com for more information.