At least 42 people have been injured in a suspected gas explosion that destroyed wooden buildings housing a restaurant and a real estate office in northern Japan, according to police and local media reports.

The powerful blast on Sunday in Sapporo, the capital city of Japan’s northern main island of Hokkaido, shook nearby buildings, broke windows and scattered wooden debris across the area.

Some residents told reporters they thought the blast was an earthquake.

One person was in serious condition, but police said the other injuries were mostly mild. Several children were reportedly among those hurt in the explosion.

“I heard a ‘bang’, which sounded like thunder, and my condo was shaken,” a man in his 50s who lived nearby told The Japan Times.

Police are investigating the cause of the blast, which hit in Sapporo’s Toyohira district.

One witness reportedly said he had smelled gas after the explosion, and the Kyodo news agency reported that a gas safety centre official noted five propane gas tanks outside of the pub and two outside the real estate office.

The fire burned for nearly six hours, Kyodo said, and photographs and TV footage showed large flames and plumes of smoke rising above charred, collapsed debris as dozens of firefighters poured water onto the building.

Windows on an apartment building next door were shattered and cars parked outside were partially covered with debris that had fallen on them.

The city government had opened a shelter to house dozens of people whose homes were damaged in the blast.