Two people were killed and two critically hurt yesterday when their private plane, aloft for a nature survey, crashed into thick woods in Ocean County, N.J., authorities said.

After the Cessna Skymaster crashed in Eagleswood Township about 4 p.m., a badly hurt passenger, Juan C. Salinas, 43, of Mexico City, used a cell phone to call 911 for help,

The pilot, John Ambroult, of Chatham, Mass., and a South Jersey woman were pronounced dead at the crash site. State police would say only that the woman was from Browns Mills in Burlington County; they said they were withholding the release of her name pending notification of her relatives.

The victims' bodies were left in the wreckage while investigators examined the plane, which ended up upside down.

Salinas and another woman, also not identified, were flown by helicopter to Atlantic City Medical Center - City Division, where they were in critical condition last night.

State police, who patrol the area, said the plane appeared to develop mechanical problems and tried to land at Eagles Nest Airport in Eagleswood but "didn't make it." The plane crashed about a 100 yards from the air strip.

The twin-engine Cessna 337A had taken off from Millville, N.J..

Ambroult owned the plane, according to records of the Federal Aviation Administration. He operated Ambroult Aviation in Chatham.

The three others in the plane worked for Geo-Marine, Inc., based in Plano, Texas. The company specializes in surveys of whales, dolphins, birds and other natural life.

On May 1, the firm announced the opening of a New Jersey office in Millvile, saying it would work on state wind-power projects and perform "ocean and wind power ecological baseline studies and groundtruthing" for the environmental officials.

Contact staff writer Craig R. McCoy at 215-854-4821 or cmccoy@phillynews.com.