Two elderly people were rushed to a hospital Wednesday evening after suffering carbon monoxide poisoning while cooking on a barbecue in a house garden in Sapporo, local police said. Their injuries were not life-threatening.

The man and the woman, both in their 70s, were cooking Mongolian mutton barbecue with two others in a kamakura snow hut built in a garden of a house in Nishi Ward at around 7:25 p.m. Wednesday, police said.

Since the flow of fresh air was limited inside the snow hut and they were using charcoal as the source of the BBQ fire, the level of carbon monoxide probably increased at some point, the police said.

The snow hut was 1.8 meters tall, 2.5 meters wide and 3.5 meters deep. The wooden door had been closed during the BBQ, the police said.

One of the four told police they had cooked similar BBQ meals safely before, and that's why they did so again.