More than 40 people have been injured in an explosion at a restaurant in the Japanese city of Sapporo.

Police said one person was in a critical condition following the blast in Hokkaido, the most northern of Japan’s main islands. Forty other people suffered minor injuries.

The cause of the explosion has not yet been established but Kyodo news agency reported that witnesses in the area could smell gas.

The blast happened in Sapporo’s Toyohira district at about 8.30pm local time (11.30am GMT) on Sunday. It caused the restaurant to collapse.

Footage posted on social media showed fire crews battling intense flames in a street strewn with debris.

“I heard a ‘bang,’ which sounded like thunder, and my condo was shaken,” a man who lives nearby told the Japan Times.

Firefighters cordoned off the area amid fears of further explosions.