Federal investigators believe the helicopter that crash-landed in the ocean near Martha's Vineyard probably had engine problems, but did not suffer engine failure.

Federal Aviation Administration spokeswoman Holly Baker says officials are trying to determine what happened to the engine, and to what degree the problems occurred. Baker says the investigation could last weeks.

Investigators moved the helicopter onto a barge Sunday to be taken to an airport on Martha's Vineyard.

The helicopter was forced to make a "soft landing" in the water about 1,000 yards north of the mouth of Lake Tashmoo on Saturday. It was traveling to the island from Norwood.

None of the four people and two dogs on board was hurt.