Five people were injured at Alki Beach Monday night after fuel – initially reported to be gasoline – was put on a bonfire, causing nearby residents to report an explosion.

Those burned were high-school age, all 18 or younger.

“They were burning high school papers when one of them decided to put some kind of accelerant on the fire and it essentially exploded back onto them,” Fire Department spokesman Kyle Moore said.

One of the teens suffered second- and third-degree burns to his arms and face, and another suffered second-degree burns to his arms. They were taken to Harborview Medical Center in serious condition.

Three others were in stable condition. A girl had burned hair and eyebrows and two other males had first- and second-degree burns to their upper chest, Moore said. They also were taken to Harborview.

Fire investigators went to Harborview to talk to the teens, and Moore said they were working with Seattle police for potential criminal case of using accelerant on a beach fire. For rules regarding Alki Beach fires, click here.

Alki Beach fire