NEW YORK (CNN) — UPDATE: Two firefighters were killed when one or more shooters opened fire at the scene of house fire in upstate New York on Monday, police said.

ORIGINAL STORY: At least two firefighters were shot when they arrived to battle a blaze at a house in upstate New York on Monday, officials said.

Authorities believe someone shot at the firefighters shortly after they exited their vehicles, said Rob Boutillier, fire marshal in the town of Webster, New York.

The gunfire stopped firefighters from battling the blaze and forced police SWAT teams to evacuate homes in the area.

Firefighters arrived at the scene before 6 a.m., Boutillier said. By 9 a.m., flames had engulfed three houses and a vehicle, he said.

Doctors were treating the wounded firefighters Monday morning, said Teri D'Agostino, a spokeswoman for Strong Memorial Hospital in Rochester, New York.

One firefighter escaped from the scene in his own vehicle about an hour after he was shot, then was transported to the hospital by an ambulance from another location, Boutillier said. He was listed in satisfactory condition, Boutillier said.

The second wounded firefighter was conscious and speaking when he was removed from the scene, Boutillier said.

Officials believe a third firefighter may have been shot, he said.

"Our main concern right now is to have law enforcement evacuate the people in harm's way (and) make the scene safe for the fire department," Boutillier told reporters. "And then the fire department will go in and do its job."

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