Fire officials say sparks from a passing train migrated to dry grass near 4400 West and 850 South causing piles of materials in nearby lots to start on fire around 7:30 p.m.

Flames quickly spread to Central Pallet of Utah and Applied Installation & Erection Inc., said Capt. Karleen Montanez of the Salt Lake City Fire Department.

The inferno created a dramatic sight as propane tanks exploded and semitrailers filled with palettes and other materials burst into flames. The fire progressed from a one-alarm fire to a two-alarm fire by the time firefighters arrived on scene, Montanez said.

Two minutes after firefighters got to the area, the fire increased to a three-alarm fire and around 8 p.m. it escalated to four alarms, she said.

No injuries were reported and no one was believed to be working at any of the businesses when the fire broke out.

An identical scenario happened at the same address two years ago, when the businesses suffered damage after sparks from a train, Montanez said.

About 100 firefighters worked to extinguish the blaze for more than three hours. By 10 p.m., the blaze was nearly contained.

The spectacle attracted hundreds of residents who saw flames from miles away and drove to streets surrounding the scene to get a front row seat to see thick, black plumes of smoke.

John Anderson of Salt Lake City found a spot on 700 South underneath the Bangerter Highway to watch the fire. He said he saw flames leaping high into the air all the way from his home near Trolley Square.

"It's a horrible fire," he said, watching as dozens of other people snapped photos on their cameras and cell phones.

Owners of the three businesses couldn't be reached for comment on Saturday, but several employees of the businesses roamed the scene to survey the damage.

Salt Lake City Fire Chief Dennis McKone estimated damage to the businesses at $500,000.

The previous major fire to cause such extensive damage in Salt Lake City was in January, when the former Club DV8 went up in flames at 115 S. West Temple.

Fire officials categorized that January blaze, which caused an estimated $1 million in damage, as the city's largest in five years.

mrogers@sltrib.com