CONEWANGO TWP, Warren County - A Butler County businessman remains hospitalized with serious injuries from a Monday afternoon airplane crash that killed his business partner.

Federal investigators continue to investigate what caused the single-engine Cessna 177 to crash off a runway at the privately owned Warren Airpark near Warren.

Pilot Duane Burtner, 53, of Penn Township, who owns the plane, was listed in critical condition this morning at Hamot Medical Center in Erie, a hospital spokesman said.

Burtner was downgraded overnight after being admitted to the hospital in serious condition.

The hospital declined to disclose his injuries; however, an eyewitness to the crash who later helped rescue the man from the plane, said Burtner appeared to have a broken leg and other injuries.

Malcolm Strachan, 45, of Penn Township, the lone passenger in the plane, was pronounced dead at the scene following the 4 p.m. crash, said Warren County Coroner Jerry Borden.

An autopsy Tuesday in Erie revealed Strachan died of "massive injuries to the head and neck," Borden said.

Results of toxicology tests would not be available for six to 10 weeks, he said.

Strachan and Burtner were partners of the firm Industrial TroubleShooters of Penn Township, a process control and instrumentation company specializing in projects for chemical and steel plants.

Strachan was president of the company he founded in 1993, according to Department of State records. Burtner is the company secretary.

The two men had left the Butler County Airport earlier Monday on their way to discuss business with officials at Warren-based Struthers Wells Corp., a firm that manufactures industrial heaters and other thermal fluid systems,

Bob Pelini, a Wells Struthers employee who was at the Warren area airport to meet the men, said the pair had flown there before on a number of business trips.

Federal Aviation Administration officials said the plane touched down on the runway that is atop a hill but it suddenly veered off.

Burtner apparently attempted to fly back up but did not attain sufficient altitude and clipped several trees. The plane crashed nose first before flipping onto its roof, said Chief Kirk Foust of the Starbrick Volunteer Fire Department.

Firefighters, ambulance paramedics and local and state police were called to the crash after Pelini saw the plane go down and called 911.

Pelini and a neighbor ran to the wreckage and found Strachan and Burtner hanging by their seat belts, upside down. After several minutes, they managed to get Burtner out of the plane before paramedics arrived.

Two FAA investigators inspected the wreckage Tuesday, and were looking into the possibility that Burtner could have diverted the landing, possibly fearing he did not have sufficient runway left to complete the landing, said FAA spokeswoman Arlene Murray.

Wind gusts were another possible factor in the crash, authorities said.

Other investigators with the National Safety Transportation Board were to be at the crash site today to take over the investigation.

The NTSB could have a preliminary report completed within two weeks.