The Inglewood Courthouse was evacuated Monday afternoon when potentially hazardous materials were found on the building's second floor, authorities said.
A man was injured after handling the substance in the courthouse, said Inspector Randall Wright of the Los Angeles County Fire Department.
County Fire Capt. Keith Mora said the man's injuries were sustained after he opened an envelope. His condition is unknown.
Initially about 15 people on the second floor were evacuated, but officials later expanded the evacuation order to cover the entire building.
This story will be updated as more information becomes available.