A 73-year-old man was killed and his wife was burned early this morning when their house caught fire in Liberty Township, Mercer County near the Butler County line, authorities said.

The 63-year-old woman was able to get her husband outside of the two-story home on the 2500 block of Mercer Butler Pike before he died, and she called 911 at about 1 a.m.

Dispatchers advised emergency crews that the call was “an explosion with fire and injuries,” said Dan Hutchins, chief of the Springfield Township Volunteer Fire Department.

Investigators, however, were unable to immediately confirm there was an explosion.

The state police fire marshal is investigating the blaze but a cause has not been determined. Fire officials have not ruled out smoking near oxygen as a possible cause.

The couple, who names were not immediately released, reportedly were smokers, authorities said.

Mercer County Coroner John Libonati pronounced the husband dead at the scene. Libonati was not available for comment.

Quality Ambulance and Slippery Rock EMS responded and medics tended to the woman before she was taken to Grove City Medical Center. From there, investigators said, she was to be transferred to UPMC Mercy hospital in Pittsburgh.

Authorities described her burns as “serious,” but she was conscious the entire time before being taken to the hospital. Her condition was not available.

“Based off of the general looks of the layout of the house,” Hutchins said, “I would say odds are (the fire) started in the (couple's) bedroom.”

He noted “there was oxygen present” in the bedroom.

The home, which was heated by fuel oil, was engulfed in flames when fire crews arrived. Firefighters used a defensive attack and deployed a tanker shuttle.

There are no hydrants in the rural neighborhood, Hutchins said. Crews utilized a hydrant about three or four miles away near the Premium Outlets in the township as their water source for the tankers.

About 75 firefighters from 10 departments battled the blaze. None of the firefighters were injured.

The fire was under control in about 90 minutes, Hutchins said. During the fire fight, unknown family members of the couple showed up.

Trooper DuWayne Baird, a deputy fire marshal, was at the scene to begin his investigation of the cause and origin of the blaze. The state police crime unit at the Mercer barracks is also investigating.

“The chances of finding out a cause are going to depend upon further investigation which is going to be interviews and a scene examination,” Baird said. “So I'm probably going to have to come out in the daylight hours again and dig around.”

A key part of his investigation, he noted, would be an interview with the injured survivor.

Assisting the Springfield VFD were firefighters from Slippery Rock and Harrisville in Butler County; Pine Township, Grove City, Mercer East End and Jackson Center in Mercer County; Scott Township and Volant in Lawrence County; and Clintonville in Venango County.