Five people were missing following a natural gas explosion that leveled half a city block in downtown Bozeman building Thursday morning.

Deputy Bozeman Police Chief Mark LaChapelle confirmed at about 1:30 p.m., that five people were still unaccounted for after the early morning explosion that destroyed four businesses. Emergency workers, though, have been unable to begin searching the rubble as the buildings in the area were still burning and unstable from the blast that was felt several blocks away.

"There is so much damage there and so much fire still that we cannot get out crews in," said Chuck Winn, assistant city manager and Bozeman's former fire chief.

Emergency workers evacuated a two-block radius from the explosion that was centered at Boodles restaurant at 215 East Main St., at 8:12 a.m. Boodles was destroyed in the blast, as were the The Rockin' R Bar, Montana Trails Gallery and the American Legion club.

Flames and smoke were still rising from the building after 1 p.m. Fire fighters were confident, though, that they would be able to hold the fire to the area between the Rocky Mountain Rug Gallery and Starky's restaurant.

"Everything between there is a total loss," Winn said.

Witnesses in the area reported seeing debris fly three times the height of the two-story historic building. Glass windows on downtown storefronts two blocks away were shattered by the blast.

City officials were centering their investigation on a gas line that runs a half-block north of Main Street, although the exact cause was still unknown.

A service line running into the East Main Street building was damaged in the explosion. It is now leaking gas and fueling the fire, said Claudia Rapkoch, communications director for NorthWestern Energy.

"It is blowing gas right now, which is on fire," Rapkoch said.

NorthWestern crews are excavating the main gas line running in the alley behind Main Street on either side of the leak, so they can plug the gas flow, she said.

"It is a long an involved process," she said.

NorthWestern does not yet know what caused the explosion which rocked downtown Bozeman, Rapkoch said.

"That is unknown at this time," she said.

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