A man making repairs with a welder had three fingers blown off in an explosion Thursday morning in the yard of an Elmont construction company, authorities said.

The victim, 61, suffered burns and other injuries on his face, chest and left hand in a blast that occurred 8:35 a.m. at a yard on Star Avenue, owned by LJC Dismantling Corp., located across the street on Meacham Avenue, according to Nassau police and the county fire marshal's office.

He was trying to repair a backhoe or another piece of heavy equipment, but investigators at the scene were trying to determine what exactly set off the explosion, said James Hickman, head of fire investigations for the Nassau County Fire Marshal's office.

"They're thinking there was buildup of gases and that he hit a pocket of gas and the gas exploded," Hickman said.

The incident was initially reported as a generator explosion and the Elmont fire department responded, but Hickman said the generator and the building did not burn and were not damaged.

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The man, whose name was not released, was taken to Nassau University Medical Center in stable condition, police said.

The blast is also being investigated by the arson and bomb squad, police said.

A receptionist at LJC Dismantling said the man is an employee.

The business provides "total demolition specialists" for controlled explosions of buildings no longer needed and clearing out of buildings to be reused, according to its website. Its crews have worked on St. Francis Hospital in Roslyn, Manhattan high-rises, Governor's Island and the Jet Blue terminal at Kennedy Airport, the company said.