WASHINGTON -- D.C. Fire and Emergency Medical Services personnel responded to the Internal Revenue Service building Tuesday morning because of a powdery substance that was found.

Fire Department spokesman Alan Etter said the hazardous-material team cleared after firefighters concluded with a "high degree of certainty" that the substance found in a letter was not anthrax.

Etter said there's a protein present, and it's a chemical similar to strychnine, however he said more testing is needed.

The hazmat team was also sent to CNN's offices in the 800 block of First Street Northeast because of a report of a suspicious package.

Etter said a letter was found to have some ammonium phosphate on it, but that is not harmful.