The cause of a fire that engulfed two Bangor apartment buildings Monday night and caused an explosion in one of them has not yet been determined.

The blaze is being investigated by the state fire marshal’s office, Bangor Fire Assistant Chief Philip Hamm said Tuesday. He declined to comment on the possible cause.

The fire began at a five-apartment complex at 11 Center Street Ave. before spreading to a two-apartment building a few feet away at 9 Center Street Ave., witnesses said. Smoke billowed from both buildings and could be seen as far away as Broadway and surrounding streets.

The fire caused what witnesses described as an explosion at 11 Center Street Ave. around two minutes after the flames erupted, said Crystal Fogleman — who lived at 9 Center Street Ave. — and Sarah Holt, who was working in a home on Center Street Avenue at the time. Numerous people nearby reported hearing a loud boom.

Holt and Fogleman described a frantic scene, with several people dashing to get out of the burning buildings. Three of the five units at 11 Center Street Ave. were occupied at the time of the fire, Fogleman said, though she was unsure how many people were living in the building.

Flames come out of a home at around 6 p.m. at 11 Center Street Ave. in Bangor Monday evening. Credit: Courtesy of Shannon Levesque

Fogleman and a man who lived in her building both had injuries. While Fogelman’s are relatively minor, the man is in the hospital for smoke inhalation, she said. One tenant in 11 Center Street Ave. lost their dog, while Fogleman’s cat suffered a noticeable burn injury on his left ear.

Holt said she was going to her car to grab a charger when she noticed a fire around the back deck of 11 Center Street Ave. that quickly spread. She banged on the door of the home to tell them what was happening.

The tenants at 11 Center Ave. quickly ran out with their pets, while Holt and Fogleman helped an older man who lived at 9 Center Street Ave. out of his home. That’s around when Fogleman and Holt felt the explosion. Fogleman said she fell to the floor.

“It took my breath away,” Holt said.

Fogleman said she took her shirt off as she left her house, as she could feel the heat on her back. She had some minor injuries but lost numerous belongings, including a TV, multiple cell phones and a purse containing her ID, social security card and medical insurance card. She has since moved into a new apartment on High Street.

She said an oxygen concentrator — a medical device that removes nitrogen from the air to produce concentrated oxygen — inside 9 Center Street Ave. also exploded about five minutes after the first explosion. While it wasn’t as loud, it was strong enough to blow furniture into the back lawn, Fogleman said.

Fogleman described the whole experience as psychologically devastating

“I”ve only slept an hour, because every time I heard the ambulance or the fire trucks, my eyes popped open,” Fogleman said. “It felt like I was back there.”