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Investigators on Monday resumed efforts to determine what caused a four-alarm commercial yard and warehouse fire in southwest Salt Lake City over the weekend.

A specially-trained arson dog failed to find traces of accelerant use in the wake of the 3:40 p.m. Sunday blaze at 879 S. Gladiola St. (3400 West), where four businesses were housed. While the cause remained undetermined, Salt Lake City Fire Capt. Mark Bednarik said it was not considered suspicious in origin.

Crews arrived at the scene to find fire had sparked into stacks of wooden pallets, trash bins and a trailer next to the warehouse, which also was ablaze.

"While fighting fire on the interior, a series of explosions caused a temporary withdrawal of firefighters for safety concerns. The small explosions continued for the next few minutes, and propane cylinders for forklifts were considered the cause," Bednarik stated. "The commercial fire sprinkler system helped contain the fire inside of the warehouse until crews were able to re-enter and extinguish it."

However, sparks also ignited fire in a nearby field, burning an acre of grass before it was snuffed.

Assisted by neighboring West Valley City crews, more than 70 firefighters brought the warehouse blaze under control by 5 p.m. Some crews remained through the night dousing hot spots and guarding against flareups.

Major fire damage, initially estimated as more than $150,000, was limited to the yard and the exterior walls of the warehouse, Bednarik said.

However, losses could mount as property owners compiled damages from smoke and water.

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