From AP:

NEWARK, N.J. – Authorities boarded an American Airlines plane Saturday 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.

They had no weapons, said Tim Smith, an airline spokesman.

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

More as it is announced (h/t: The Jawa Report)

UPDATE: Little is being reported online or on the cabel news networks. The only thing I could find in addition to the AP story quoted above is one line found on News Watch 50 WWTI NY saying that, ” The FBI is expected to take over the investigation.”

UPDATE II: WBAL TV, Baltimore, is reporting that the five have been released.

Five men who had been detained Saturday afternoon after an American Airlines plane landed at Newark Liberty International Airport were released by Saturday evening, federal officials told WNBC in New York.

[...]

By Saturday evening, there was still no official comment on why the men were detained. But the men had all been all reading helicopter flight manuals onboard the plane, which raised suspicions of flight attendants, passengers and air marshals.

Via Newsday:

ive men briefly detained Saturday after an American Airlines flight landed at Newark Liberty International Airport were found to pose no threat and were later released, an FBI spokesman said.

The men _ identified only as four Angolan military personnel and an Israeli _ were traveling back to their respective home countries after attending helicopter training school in Texas, said Steven Siegel, a spokesman for the FBI’s Newark office.

Fellow passengers on Flight 1874, which had departed from Dallas Fort Worth International Airport, became suspicious of the men because they were speaking in foreign languages and had “aircraft flight materials” with them, Siegel said.