Update: 11:12, a.m.: The building has been reopened, authorities said. No injuries were reported.

Update, 11:09 a.m.: The streets were reopened to traffic late Friday morning, according to authorities.

Original post: D.C. firefighters and federal authorities are investigating a suspicious package that contained white powder at the U.S. attorney’s office at Judiciary Square in Northwest Washington.

FBI Special Agent Jacqueline Maguire, a spokeswoman, said the building in the 500 block of 4th St. NW, near the District’s courthouses and police headquarters, was on lock down as of 10:40 a.m.

People were told to remain in their offices, Maguire said. She could not identify the specific office in which the package was found.

Battalion Chief Brandon Lee, a D.C. Fire Department spokesman, said four people were exposed and were being evaluated. He said authorities have not yet identified the substance.

D.C. police closed the intersection of 4th and G streets and closed E and F streets between 3rd and 4th streets to pedestrians.

This item has been updated.