STRATFORD, Conn. (AP) _ A military helicopter crashed in a ball of flame this morning on the grounds of Sikorsky Aircraft, state police and witnesses said.

No deaths had been confirmed. However witnesses said it appeared there was no way anyone could survive. A local radio station reported a crew of four was on board.

Sikorsky officials reported the crash about 11 a.m., said state police Trooper Aaron Haley. He said medical crews and other authorities were on the scene.

It was unclear whether the helicopter was trying to land at the plant, which makes military helicopters, or had just taken off, Haley said. Witnesses said it was hovering 100 feet to 200 feet above the end of the tarmac, and appeared to be in trouble.

``I saw the helicopter hovering ... like it was trying to get up. ...,'' witness Jeff Kunkel told New Haven television station WTNH-TV. ``The next thing I know this thing hits the ground and parts and everything went flying all over the place and it burst into flames.''

Another witness told Bridgeport radio station WICC the helicopter crashed in a fireball about 15 feet from the Housatonic River, which runs alongside the Sikorsky plant.

Sikorsky did not immediately return phone calls from The Associated Press.

The crash caused massive traffic jams on the nearby Merritt and Wilbur Cross Parkways, as motorists slowed down to watch the accident.

``I saw it start going up, and the next thing there was a big boom _ it shook our building, it crashed, and there was smoke billowing out all over,'' said Mary Beth Desrosiers, a clerk at Oronoque Pharmacy across the street from the plant.

John Stein, a cashier at the pharmacy, said the helicopter was a few hundred feet off the ground before it crashed.

``There's pieces all over the place. Big black smoke everywhere. Quite an awful thing,'' Stein said.