CLINTON TOWNSHIP, Mich. (AP) — A large fire followed by multiple explosions at a building in suburban Detroit killed one person and injured a firefighter.

A look at what we know about the site, including investigators’ questions surrounding the vaping supply distributor operating there.

WHAT CAUSED THE EXPLOSIONS AND FIRE?

Authorities believe canisters containing gas chemicals may have been responsible for the repeated explosions reported by first responders and witnesses. They haven’t yet determined the cause of the fire. The federal Bureau of Alcohol, Tobacco, Firearms and Explosives is among those investigating.

The building housed a distributor for the vaping industry called Goo, and canisters stored inside contained nitrous and butane, said Clinton Township Fire Chief Tim Duncan. The size of those containers wasn’t immediately clear.

The business wasn’t permitted to have those materials, Township officials said Tuesday. Duncan said the last inspection of the site in 2022 “did not show this amount of material.”

Duncan said a truckload of butane canisters had arrived within the past week at the building and more than half of that stock was still on site when the fire began. There were also more than 100,000 vape pens stored there, the fire chief said.

The Associated Press left phone and email messages with Goo on Tuesday.

Owners and employees are cooperating with investigators, said Clinton Township Police Chief Dina Caringi. Authorities and witnesses described repeated booms that even shook nearby cars as the gas canisters exploded; some canisters were found embedded in neighboring buildings.

Ben Ilozor, a professor of architecture, construction and engineering at Eastern Michigan University, said the size and strength of the fire made sense after he learned what was on site.

“All of the vape pens are missiles,” he said. “All of the canisters. It’s a missile. As they are catching temperature, they are exploding and combusting, and that’s why it wouldn’t just happen at once. It would be continuous, depending on the level of heat they are exposed to.”

Butane is highly flammable; nitrous can increase a fire’s intensity and explode when heated inside a container. The failure of lithium batteries like those in vaping and e-cigarette devices is another known fire hazard.

WHAT CAUSED THE DEATH AND INJURY?

Authorities believe the man was watching the fire when one of the canisters struck him after traveling a quarter of a mile from the building. The firefighter was believed to be injured by glass after one of the canisters hit the windshield of a vehicle.

IS THERE STILL DANGER?

Clinton Township officials asked residents to stay away from the site and said it would be fenced off and guarded as cleanup begins. But there is no sign of dangerous air quality in the area, Fire Chief Tim Duncan said Tuesday.

A spokesman for Michigan’s Department of Environment, Great Lakes, and Energy said Tuesday that air monitoring by local hazardous materials crews “did not detect anything concerning.”