NEWARK, N.J. — A United Airlines flight had to return to Newark Airport Monday morning amid concerns about a strong odor in the cabin, the FAA said.

United Flight 1704 departed at 6 a.m. for Austin, Texas, but about 20 minutes after takeoff, it returned to Newark. The crew aboard the Boeing 739 had reported a strong odor in the cabin, according to the FAA.

The plane landed safely. An investigation is underway.