Bangor firefighters faced a highly dangerous situation late Sunday afternoon when they were called to put out a fire in a tractor-trailer box filled with gas tanks at Bangor Welding Supply on Outer Hammond Street.

The fire, which threatened two other trucks filled with tanks and the main building, was quickly brought under control, and it then extinguished itself, according to Assistant Chief Scott Bostock of the Bangor Fire Department.

The tanks continued to leak after the fire was over, and a fire crew was expected to stay at the scene throughout the night, said Bostock.

Traffic in the vicinity was blocked off for more than two hours.

“You had a very volatile situation with a lot of product,” said the assistant chief. “If the fire had extended into the building, we would have had a major incident. The potential was there for a very dangerous fire.”

Pointing out that there were two large cylinders of oxygen on the side of the building, Bostock also said that “had that building been burning, I would have evacuated everything within a half-mile.”

The cause of the fire is under investigation. Bostock said he planned to call in the state Fire Marshal’s Office because it was “a unique kind of fire, not something we deal with every day.”

Several people called in the alarm at 5:40 p.m., said the assistant chief. Firefighters found the fire burning in the trailer box, which was parked against the building at a loading dock. Fire was showing through the middle and the top of the trailer, said Bostock.

The department responded with a crew of 12 firefighters and two engine companies, one aerial ladder and one ambulance. No one was injured while fighting the fire, said Bostock.

The trailer box was filled with about 80 tanks containing different types of gases, including acetylene, liquid propane, nitrogen, and oxygen. About 30 of the acetylene tanks were burning, said the assistant chief.

In addition, two flatbed trucks loaded with cylinders were parked next to the trailer.

“The tanks on one truck were steaming, so we had to cool down those tanks and cool the tanks in the box,” he said, adding that the firefighters kept pouring water over the tanks.