STOW CREEK TOWNSHIP, N.J. (AP) _ Two men testing a helicopter before delivery to the U.S. Army were killed when the machine crashed in a marshy area near the Delaware Bay, officials said.

Two other crew members parachuted to safety shortly before the crash Thursday.

Killed were Donald Vetter, 42, a co-pilot from Wallingford, Pa., and Raymond Fright, 59, a flight test engineer from Morton, Pa., said Bob Torgerson, a spokesman for Boeing Vertol, which was testing the aircraft.

Charles J. Schluck, a 37-year-old flight test engineer from Drexel Hill, Pa., was examined at Salem County Memorial Hospital and released, state police said. Albert Freisner, a 48-year-old instructor pilot from Wallingford, Pa., was treated for a cut on his chin.

Torgerson said the aircraft was a Boeing CH47-D, also known as a Chinook. Torgerson said variations of the model have been in the Army inventory since the 1960s.

Boeing Vertol has been in the process of modernizing the Chinook, a transport aircraft with a capacity of 25,000 pounds, and has been delivering the upgraded helicopters to the Army at the rate of four a month, Torgerson said.

''The aircraft was on a routine test flight prior to delivery for the Army,'' Torgerson said.

All four men worked for the Ridley Park, Pa., company, Torgerson said.

The helicopter crashed shortly after 11 a.m.

Harry Duffield, a crabber from Lower Alloways Creek, said he was docking at a boat ramp about one-half mile away when his father told him to ''look at the chopper.''

''I looked around and it was going down nose first,'' said Duffield, adding that flames were shooting out from the aircraft. Duffield said he looked again and saw two parachutes floating to earth.