BANGOR – Two firefighters were considered “very fortunate” to have survived an explosion while they fought a blaze at 193 and 195 Pine St. about 6 a.m. Thursday that left four families homeless.

Doug Holland and Bill Wentworth were treated for minor burns on their legs after an explosion blew out the windows of a second-floor apartment and ignited everything inside while the firefighters were entering the building.

Their injuries were suffered when the building “flashed over,” said Bangor Fire Department Assistant Chief Rick Cheverie.

A “flashover” occurs when temperatures in a room exceed 1,500 degrees Fahrenheit, causing objects in the room to emit gases, the assistant chief explained. When oxygen reaches such gases a fiery eruption ensues, he said.

“People do not usually survive flashovers, even firefighters in their gear,” said Cheverie. “We’re fortunate, very fortunate.”

Firefighter John Gray also was injured while fighting the fire. The extent of the injuries to his back after he “wrenched it” were unknown Thursday night, said Cheverie. Several other firefighters reported cuts and bruises after the three-hour battle with the blaze that was under control by 9 a.m.

Bob and Terry Butler, residents of the apartment where the fire apparently began, were treated for minor burns and released from Eastern Maine Medical Center, according to Cheverie. The couple had left the building before the explosion.

On Thursday night, investigators were focusing on what was the living room of the couple’s second-floor home.

Firefighters were told that one person still was inside when they arrived at the burning building.

Timothy Abbott, Rebecca Carpenter and their daughter in Apt. 5, the Butlers in Apt. 2, and Al Seidus and Cynthia Phillips in Apt. 1 all reached safety before firefighters arrived.

Officials were told that 52-year-old Gerald Johnston was still in Apt. 3, located at the back of the first floor, said Cheverie.

Two rescue efforts were made to save Johnston before fire officials discovered that the man had left for work at the Community Health and Counseling Services an hour earlier than usual, according to the assistant chief.

“I thought my dad was still in the house. I was hysterical,” said Marsha Thibodeau, who lives in an apartment next door and woke up as the building “flashed over.”

Johnston did lose his three cats – Bednight, Morris and Gremlin – in the fire, he said Thursday night from his daughter’s apartment where he is staying.

Other residents of the apartment building had made arrangements through the American Red Cross or family members for places to stay, said Cheverie.

More than 23 firefighters and medical personnel responded to the emergency call. Damage to the building is estimated at more than $200,000. While many of the apartments received heavy smoke and water damage and minimal fire damage, the Butlers’ home was destroyed, said Bangor Fire Department Assistant Chief Darrell Cyr.

The cause of the fire is still under investigation, said Cheverie. Two state fire marshals were brought to the scene later Thursday evening.

The “balloon” design of the building gave the fire easy access to go wherever it wanted to go, said Cheverie.

“It traveled all over and any which way it wanted,” he said.

The building, which is owned by Dale Belcher of Bangor, was insured, Cheverie said.

Those who want to aid the families who lost their homes in the fire may contact the American Red Cross at 941-2903.