Japanese media said that police are investigating the cause of the explosion, suspected to be a gas explosion. The incident occurred at around 8:30 p.m. local time at izakaya Umi Sakura, near Hiragishi Station on the Sapporo metro line.
Japanese media said there was no information about any deaths. Of the 42 people injured in the explosion, 41 were slightly injured and 1 was seriously injured.
The explosion caused the 66-seat bar to collapse and shocked the windows of nearby apartments, food and beverage stores.
Hiragishi is less than a 15-minute train trip from the main station of Sapporo, the capital of Hokkaido, northern Japan.
The Hokkaido Police Department and other emergency rescue forces have ordered diners and nearby residents to evacuate amid warnings of the possibility of further explosions.
According to images from NHK, at 8:00 p.m., the fire was still burning fiercely, firefighters were trying to control the fire while other forces were evacuating restaurant staff and diners.
Locals compared the sudden explosion to a strong, thunderous earthquake and a missile attack. Passersby said they smelled a strong smell of gas.
Mainichi daily quoted a 70-year-old resident as saying: "The restaurant completely disappeared without a trace, the roof of the restaurant owner next door also collapsed. I don't know what to say about how I feel about this tragedy."
NHK quoted the sister of a restaurant employee among the injured as saying that the victim jumped from the 2nd floor and broke her leg. "I am grateful that my brother is alive" - this person said.
