A United Airlines flight bound for Las Vegas was forced to return to Newark Liberty International Airport for an emergency landing early Tuesday morning after the crew reported possible engine trouble, the Federal Aviation Administration said.

The Boeing 757 took off from Newark but landed safely back on the runway shortly after 6:30 a.m.

The FAA stated the crew detected potential issues with the engine, prompting the return.

All 176 passengers and six crew members emerged unharmed.

The exact nature of the engine problem was not disclosed, and further details were not immediately available.