Passengers were forced to evacuate a United Airlines plane at Reagan National Airport on Sunday after smoke was reported in the cabin, authorities said.

The Metropolitan Washington Airports Authority said that about 1 p.m. Sunday, Houston-bound flight 6122 was taxiing for takeoff when emergency crews were called for a report of smoke in the cabin. The plane’s emergency slides were deployed, and all passengers and crew members exited “without incident” and continued to the gate, MWAA said.

Washington Post reporter Philip Rucker shared video from the terminal showing passengers sliding onto the tarmac from the United plane, which was surrounded by three fire engines and two ambulances.

“Normal airport operations have resumed, and the aircraft is being checked by airline personnel,” the airports authority said.

United said the issue affected a Mesa Airlines flight operating under the United Express brand. Passengers safely evacuated the plane, United said. The cause of the smoke was not immediately known.

“We are currently investigating the cause and are working with our team to secure alternate flights for customers onboard,” a United spokeswoman said.