Firefighters battled an explosive fire in a large garage in the alley behind a house at 1913 Alderson and a busy casino in Billings Monday morning.
The first of four fire engines and a ladder truck arrived at 9:37 a.m. to find large balls of fire rolling from the garage.
The fire was contained in about 10 minutes, said Billings Fire Battalion Chief Darrek Mitchell. Fire officials estimated damage to the structure at $40,000.
Onlookers, including some who had been gaming at the nearby Rio Grand Casino on Grand Avenue, reported seeing colorful explosions shoot from the garage, guessing the structure may have contained fireworks.
Fire officials said it was too early to confirm what caused the explosions or the fire.
The blaze sent up a large column of black smoke that caused traffic to back up in both directions on busy nearby Grand Avenue.