The fire was still smouldering Sunday morning after crews spent the night working on the blaze. (CBC)Investigators will be looking into what caused an explosion and fire in a building storing lithium batteries waiting to be recycled at a plant near Trail, in southeastern B.C.

Firefighters were still mopping up Sunday afternoon from the blaze that began Saturday evening at the plant owned by U.S.-based Toxco Inc. and spread to an adjacent municipal recycling facility.

"The fire's under control," said John MacLean, administrative chief of Kootenay Boundary Regional Fire and Rescue.

"They're actually in cleanup stages; they're putting out the last few hot spots on the site."

RCMP said stored lithium batteries exploded after a fire started in a small underground building at the plant.

The flames quickly spread next door to bundles of plastic and cardboard at Alpine Recycling.

Cause of fire unknown

The fire began Saturday evening, causing a series of explosions at the battery recycling plant. (CBC)Steve Low, who lives a few kilometres away, said he heard several blasts at about 5 p.m. PT Saturday and saw smoke and flames.

MacLean said no injuries were reported but the fire triggered a release of poisonous sulphur dioxide gas.

The deadly gas apparently dissipated quickly and no evacuation was ordered by Environment Ministry officials monitoring the air, said MacLean.

"The advice that they provided to us was that the best idea for people was to actually shelter in place, to stay at home, to avoid breathing the contaminants that were getting in the air," he said.

The nearest home across the road from the plant was upwind of the smoke plume but several homes are located above the industrial park 700 to 800 metres away, MacLean said.

There's no indication yet of what caused the fire, said MacLean.

Lithium batteries are used in a variety of electronic devices, especially mobile phones and portable computers. They have been known to overheat when in use, sparking fires.

MacLean said fire investigators will probe whether the stored lithium batteries ignited spontaneously.

"That's something we're definitely going to look into," he said.

Toxco's website says the incoming lithium battery waste is stored in concrete storage bunkers covered by earth.

Fire caused minor damage

MacLean said 52 firefighters and 11 pieces of equipment were battling the fire at its height and the department activated the regional district's emergency operations centre.

"We did have to request some aid from the city of Castlegar under our mutual aid agreement," he said. "What they brought was foam to assist in putting out the fire at the municipal recycling facility."

The fire at Toxco was restricted to one building, while the blaze at the municipal recycling plant mostly consumed bales of cardboard and other recycled materials stored outside and caused minor heat damage to a nearby building.