WASHINGTON (AP) — Authorities issued a shelter-in-place order and began searching Senate office buildings near the U.S. Capitol Wednesday afternoon amid reports of an active shooter.

The U.S. Capitol Police announced on the X social media platform that the security response was prompted by a “concerning 911 call” regarding a “possible active shooter.”

At 3:30 p.m., a spokesperson for the Metropolitan Police department said authorities had not immediately located any victims or other evidence of a shooting, but were still working to fully clear the area.

Inside the Russell Senate Office Building, officers evacuated the hallways and shouted at people to run outside and away from the building. Outside, tourists watched as dozens of police cars surrounded the area.

Staff and journalists working in the building received an email instructing them to take shelter in a locked room, remain quiet and silence all electronics.

Both the House of Representatives and the Senate are currently on recess and the office buildings are generally less crowded than usual.