SEATTLE - A big explosion and fire destroyed three buildings, damaged several others, sent debris flying for blocks, and jolted people awake early Friday in a Washington town, firefighters and North Bend residents said.

About the only good news was the time - 3:45 a.m. - when few people were in the business district of the Cascades foothills town about 30 miles east of Seattle.

"We are very, very fortunate that it happened in the early morning," said Josie Williams, public information officer for Eastside Fire and Rescue. "If it was two hours later, the street would have been very busy."

A couple of minor injuries were reported at an assisted-living facility where windows were blown out, she said.

It could take days to investigate the cause and estimate the value of the loss, she said.

It appears to be a natural-gas explosion, said Puget Sound Energy spokesman Andy Wappler. A utility crew responded and shut off gas to three burning buildings, he said.

The blast also knocked out electrical service in the morning to about 1,500 customers, Wappler said.

The utility is working with the fire department and state Utilities and Transportation Commission investigators with information about natural-gas service.

The building that exploded was not an active worksite for Puget Sound Energy, and contractors don't always notify the utility, Wappler said.

"There was significant damage to multiple buildings," Wappler said. "It's a reminder to folks: If they smell natural gas, leave the building and call 911."

The blast leveled a former pizza restaurant under renovation. It also destroyed a barber shop and a separate building with three offices in the strip mall, Williams said. Debris was thrown 200 to 300 feet, blowing out windows and crumpling doors at a gas station and tire store. Flying debris also broke windows at a nearby apartment.

The manager of the gas station was one of the few people awake at the time. The manager heard alarms going off from the building before it exploded and called 911, Williams said.

The blast awakened North Bend residents, including three firefighters at the station about two blocks away, Williams said. In all, about 80 firefighters from various departments responded as the fire went to two alarms.

Residents told KOMO News and KIRO-TV that they thought it might have been an earthquake, as houses rocked enough to knock pictures off walls. One woman said she heard the blast five miles away.

A nearby school was able to open as scheduled Friday, and residents were allowed back into the area after the fire was out and the area cleared.

"There was a lot of debris all over the road," Williams said. "It was huge. We're so fortunate it was early in the morning and not a couple of hours later."