The entrance to the Supreme Court was cordoned off by authorities and its ventilation system was shut down, but the offices were not evacuated.
Capitol Police Chief Kim Lettner said preliminary tests conducted at the site were inconclusive but indicated a "low risk" that the substance was hazardous. The material was transported by state police to a lab for further analysis, she said.
Lettner said the worker was alone on the sixth floor when he opened the envelope. The worker immediately washed his hands, called Capitol Police and isolated himself until the Virginia State Police and the Richmond Fire Department hazardous materials teams arrived, she said.
She said she had no further details about the envelope.