Nearly 140 people were injured today when a Long Island Rail Road train packed with commuters collided with an empty Amtrak train in a tunnel near Penn Station.

Passengers, some of whom had been standing, reported being flung through the air upon impact. Six people were seriously injured and another 130 suffered minor injuries, authorities said.

Most of the passengers suffered injuries to the head, neck and back, said Brian Dolan, an LIRR spokesman.

"I was in the process of standing up and was thrown over the seat in front of me," said Mike DeBiase, 24, of Middle Island.

DeBiase, who complained of neck and shoulder pain, said he was sitting in the last car of the LIRR train, the 5:42 a.m. from Ronkonkoma, which had been due to arrive at Penn Station at 7:02 a.m.

The LIRR said the collision happened shortly before 7 a.m. at the "JO interlocking" in a tunnel outside the east end of Penn Station.

Although railroad officials had not yet figured out exactly what happened, people who were on board the LIRR train told reporters that their train was at a stop in the tunnel and was hit from behind by the Amtrak engine.

"We were at a full stop waiting for the signal and an equipment train rammed us