Part of a street near the White House was shut down Sunday afternoon while hazardous materials specialists investiated an “undetermined substance” in a backpack, authorities said.

The incident occurred around 5 p.m. in the 400 block of 19th Street NW, near the Mall, federal offices and Constitution Hall. The site is two or three blocks from the western edge of the White House grounds.

The DC fire and ems department said one person was treated at the scene after possible exposure to the contents of the bag.