WASHINGTON -- A light, oily substance was spilled along the base of the Vietnam Veterans Memorial, and U.S. Park Police said they are investigating.

Park Police said they were notified of the substance at about 5 p.m. on Friday. It was along the base of several panels.

The National Park Service will clean up the substance, police said. The Park Service said they expect to be able to clean up all of the substance.

Park Police are investigating but said it is unknown if the spill is a criminal act.

"The care and security of this national treasure remain a top priority to both the Memorial Fund and the National Park Service," said Jan C. Scruggs, the founder and president of the Vietnam Veterans Memorial Fund. "While it is unclear what transpired, we are heartened by the response of the veterans' community and the general public."

Anyone with information about the spill should call the Park Police tip line at 202-610-8737.