Police said the boys admitted to consuming alcohol and smoking marijuana prior to falling asleep while a nearby campfire was still burning.
Emergency crews responded to the fire shortly before 1 a.m. in the area of 17215 Erie Drive.
Five teens were originally at the scene and had built a fire pit with cinder blocks, said Sgt. Matt Wildfong of the Ottawa County Sheriff’s Office. Spring Lake Fire Chief Brian Sipe said the fire pit was built inside an 8-by-10-foot structure, which was built about 2 feet above the ground.
Three of the boys went home while the other two stayed in the fort. The plan was for one of them to stay awake and tend to the fire, Wildfong said, but both boys fell asleep on a mattress in close proximity to the fire. The mattress caught on fire and the tree house was engulfed in flames.
The boys were able to escape, but they suffered second- and third-degree burns, according to Wildfong. The boys were taken to a local hospital with what was believed to be non-life-threatening injuries.
The incident is still under investigation.