A detailed report on the April 20 emergency evacuation of the US Capitol raises new questions about poor communication at a command post designed to ensure security in the skies above Washington.

A US Capitol Police official assigned to help monitor aircraft near Congress knew that the plane was authorized to be in the area and wasn’t a threat, and tried to notify colleagues in a phone call, the report by the Federal Aviation Administration said.

The evacuation—which sent hundreds of people fleeing the Capitol on an April afternoon—occurred shortly after the conversation, the report said. The report was contained in a packet sent to Capitol Hill and was viewed by Bloomberg News.

The flight that prompted the alert was being operated by an Army parachute team that had been given permission to fly over the Washington Nationals baseball stadium a short distance from the Capitol. It had received FAA permission for the flight.

The FAA findings confirm earlier reports that the aviation agency also failed to provide advanced warning to the Capitol Police and prompted an apology from its acting chief, Billy Nolen.

“On behalf of the Federal Aviation Administration, I sincerely apologize for the unfortunate confusion created by the unusual military operation on April 20, 2022,” Nolen wrote in a letter dated Friday to Speaker Nancy Pelosi. “I recognize that this caused unnecessary stress on you, other members of Congress and their staff, residents, and members of the American public visiting the Capitol area.”

Capitol Police spokesman Tim Barber declined to comment on the report.

The police officer who was monitoring the flight was at the National Capital Region Coordination Center, one of the facilities designed to protect against another Sept. 11-style terrorist attack.

The Capitol Police also didn’t notify the Domestic Events Network, which was established after the 2001 hijackings to coordinate emergency air-traffic alerts, “throughout the incident,” the report said.

Reuters earlier reported information from the report.