An American Airlines jet bound for Dallas in Texas returned to Houston Airport shortly after takeoff because of what an airlines spokesman called 'a security incident' on board.

An FBI spokesman said there may have been an attempted hijacking.

Passengers allegedly saw two men in the cabin with what appeared to be a weapon, possibly a folding knife.

The reports said the men were taken into custody.

An airline spokesman said that two US air marshals were on the flight, as were four crew members and 50 passengers.