A Boeing 767 plane flown by Delta Air Lines lost an emergency slide on Friday, prompting it to return to New York not long after taking off, officials said.

The flight, Delta Air Lines 520, had left Kennedy International Airport in New York and was headed to Los Angeles when its crew discovered an issue related to the aircraft’s right wing emergency exit slide. Crew members also detected an unusual sound near the wing, Delta Air Lines said.

Pilots declared an emergency to air traffic controllers and the flight returned to Kennedy and landed safely, the airline said.

After the plane landed, it became apparent that the aircraft’s emergency slide had “separated” from the plane, Delta Air Lines said. The plane was removed from service and the airline said it would “thoroughly evaluate the aircraft.”

“Delta flight crews enacted their extensive training and followed procedures to return to J.F.K.,” the company said in a statement, adding that it would “fully cooperate” with retrieval efforts and investigations.

It was not clear on Saturday what caused the slide to detach or where it had fallen.

The Federal Aviation Administration said on Friday that it would investigate what happened.

The flight, which had been scheduled to take off at 7:15 a.m., returned to the airport at 8:35 a.m. after its crew reported “a vibration,” the F.A.A. said in a statement. The 176 passengers disembarked and traveled to Los Angeles on a different plane.

Slides have previously fallen from planes while midair. In July, an emergency slide from a United Airlines-operated plane crashed into a home near O’Hare Airport in Chicago. In 2019, a slide from a Delta plane fell into a yard in Massachusetts.

A spokesman for Boeing referred inquiries about the plane that lost its slide on Friday to Delta Air Lines. That plane, a version of the Boeing 767, was manufactured in 1990.