An explosive fire kept firefighters busy overnight and through much of the early morning at a commercial building in the 20500 block of the Langley bypass.

Crews finished putting out hot spots at the building between 7 and 8 a.m. on Wednesday.

In daylight, passersby can see sky peeking through the building’s front windows because its roof collapsed.

The blaze began shortly before 10 p.m. on Tuesday, and the collapsed roof made it dangerous for firefighters attempting to fight it.

Several explosions occurred as the fire grew. Crews said they were likely caused by acetylene tanks inside the building. Acetylene is commonly used as a source of fuel for cutting torches.

Smoke and fire could be seen and heard as far away as Langley Hospital, and some paramedics there came down to the building to see what had gone wrong.

At the height of the blaze, 35 firefighters had been called in from both Langley City and Langley Township fire departments.

The destroyed building was home to several industrial tenants, and its size made it a challenging place for firefighters to work.

“These types of buildings are always challenging because you don’t know what’s in them,” said Kelly Gilday, deputy fire chief for the City of Langley. “They’re really large in size and so we don’t know what doors are in place and how the fire’s traveling through the building.”

The building’s tenants told CTV News this is the second fire that’s occurred in the complex in recent years.

Barbara Ferraby works at Pacific Radiator, one of the companies with offices in the building. She said she’s not sure yet how the fire will affect her business, which also has space in a nearby building that was unaffected by the blaze.

“My first thought was, that’s two in less than a year,” she said. “You kind of wonder if somebody’s setting fires.”

Firefighters said it’s too soon to determine the cause of the fire, and since the blaze burned so hot for so long, the evidence of how the fire started may have burned up with it.