Update for 6/12
The Seattle Fire Department provided an update on yesterday's Alki Beach burn victims, confirming the fire was caused by a teenager pouring an accelerant (gasoline) into the BBQ pit, which exploded and caught several people on fire.

Two male teenagers were taken to Harborview hospital in serious condition with 2nd and 3rd degree burns to their face and arms.

Two other males and one female were taken to Harborview in stable condition, the males having suffered 1st and 2nd degree burns to their upper chest. The female's hair and face were burned.

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Original post on 6/11
Five students from the Federal Way area were injured Monday night when one young man poured gasoline into an envelope and placed it into a fire ring on the beach. The envelope exploded and sent flames out in a burst and caught shirts on fire. The incident happened near 59th and Alki Avenue SW.

Three students were burned and two were injured by sparks and cinders.

Seattle Fire Department Battalion Chief S.A. Yurczyk said of the young man, identified by witnesses only as "Marshall", "That individual was burned significantly on his arm hands upper body and face. That individual was transported to Harborview. A second individual was also transported by medic unit for ALS (advanced life support) type injuries. None of them are in threat of dying but pretty significant burn injuries. Mainly arms and face and chest."

Three were transported to the hospital. Two others were treated at the scene.

Students interviewed by the West Seattle Herald said they were not expecting the fire to erupt as it did but the burst of flames affected those on the downwind side of the fire ring the most. One young man dropped and rolled in the sand and the other could not remove his shirt. Friends rushed to his aid with ice and water as others called 911.

The Seattle Police Department’s Arson Bomb Squad detectives were notified of the case.