Authorities on Saturday boarded an American Airlines plane and detained five men after it landed at Newark Liberty International Airport, according to a spokesman for the airport's operator.

The plane was bound from Dallas Fort Worth International Airport when an air marshal notified authorities of five men he considered suspicious, according to Marc LaVorgna, a spokesman for the Port Authority of New York and New Jersey.

Port Authority police took the five men into custody immediately after the plane landed at 3:20 p.m., LaVorgna said.

LaVorgna did not have more details on why the men were considered suspicious. The five men remained in custody at the airport Saturday evening. The FBI had been notified and were expected to take over the investigation, LaVorgna said.

All other passengers on the plane had been released.