Six members of a family were killed and six others were injured after a fire tore through their apartment in Riyadh on Sunday morning, authorities said.

Smoke from the burning furniture caused the six victims to suffocate to death, the Civil Defense tweeted.

The blaze broke out just after 1 a.m. on the upper floor of a two-story commercial and housing building in Al-Uraija District.

A family of 12 lived in the apartment.

A large Civil Defense team arrived at the scene only a couple of minutes after receiving a call about the fire at 1:21 a.m., said Maj. Muhammad Al-Hamadi, a spokesman for the Riyadh Civil Defense.

The crew controlled the blaze soon and saved the other six family members.

A preliminary investigation shows that the fire originated in a room spanning 20 sq. meters, while the family was sleeping, the official said.

“The furniture, made mostly of sponge, facilitated the spread of the fire and smoke inside the apartment,” he added. The six injured were sent to hospital. One of them sustained severe burns to the face, he said.

The Civil Defense has advised the public to be cautious at home and to monitor the activity of their children inside the house. “Please make sure to disconnect power from unnecessary devices before going to bed and avoid overloading electric extension sockets,” Al-Hamadi said.