One woman was killed and two of her siblings, all in their 60s, were saved early Wednesday when a two-alarm fire broke out in the second floor of a Fitchburg home.

A dramatic rescue effort began when four Fitchburg police officers kicked down the doors to get into 176-178 Walton St. The city’s fire chief, who was then off-duty, joined with a police officer to rescue a man from the burning building.

Fitchburg Police Captain Steven Giannini said police got a 911 call reporting the fire, and police sent four officers to the two-family home, where two went to the front and a pair went to the back.

The officers kicked in the doors and searched the first floor — where no one was found — before being driven out by increasing volumes of black smoke.

As firefighters arrived, two officers went back inside and tried to reach the second floor from a front stairwell, but were blocked by household debris and forced to leave a second time because of smoke, he said.

“The visibility was down to zero,’’ Giannini said.

Meanwhile, Officer Michael Faucher and Fire Chief Kevin D. Roy, who lives nearby and was in civilian clothes, rushed up a rear stairwell and into the second floor where they found a man who had passed out.

While on the stairway toward the exit, the man awoke and told his rescuers that two women were still inside, according to Giannini and Deputy Fire Chief David Gravel.

“All of this was done without any special equipment on,’’ Giannini said.

Roy alerted arriving firefighters, who sent two teams of firefighters into the blaze searching for the two women, he said.

“We immediately dispatched three fire crew members for rescue purposes,’’ Gravel said, and they were found shortly after.

One woman was found alive in the living room in the front of the house. She was carried out of the building by firefighters and then rushed to a hospital.

However, a woman who was in a bedroom in the rear of the house — which is also where investigators believe the fire started — was pronounced dead at the scene, Gravel said.

The state fire marshal’s office is looking into the cause of the blaze, which is not believed to be suspicious.

The names of the victims, all of whom were in their 60s and were siblings, were not released pending notification of relatives.

No firefighters were injured battling the blaze, Gravel said. He said arriving firefighters did not hear any smoke alarms sounding.

Jennifer Mieth, spokeswoman for the state fire marshal’s office, said a battery was found on top of a smoke alarm inside the home.

Mieth said four people have died in fires this year in Massachusetts.

“In all of the fires, there were no working smoke alarms,’’ Mieth said.

Two people died in a fire in Groton and a woman died in a house fire in North Andover this year, officials said.

John R. Ellement can be reached at ellement@globe-.com. Follow him on Twitter @JREbosglobe.