Here’s a potential recipe for disaster: a pair of unsupervised teenagers, model rockets, gunpowder and a propane torch.

Those elements led to an explosion in a North Seattle home on Feb. 16 that left two 13-year-old cousins with burns, shrap­nel wounds and temporary hearing loss, according to Seattle police.

Fortunately, the teenagers’ injuries were only moderate, police said.

A recently released police report provided details of the 10:50 a.m. explosion that ripped through a residence in the 2200 block of North 106th Street and blew out the home’s front windows.

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When officers arrived, they found Seattle Fire Department medics treating the boys, according to the report.

“I could see that both boys were bleeding, and they had what appeared to be multiple shrapnel wounds across the front of their bodies,” an officer wrote.

The officer said that cannon fuses, a bucket containing plastic and metal items, a pipe, small carbon-dioxide cylinders and a partially burnt book on model rocketry were strewn across the living room.

According to police, the adult in the house — the father of one of the boys and the uncle of the other — said he had purchased the various components on the Internet after his son became interested in model rocketry as a result of a school science project.

The boy was not supposed to work with the materials unless he was being supervised, the father told police.

On that morning, however, the father was sleeping late when the boy and his visiting cousin began to experiment, police said.

The boy told police “that he had decided to test a new rocket fuel mixture without notifying his father,” according to the report.

Police said the boy held a tablespoon of his “new formula,” which included gunpowder, in the fireplace and ignited it with a propane torch.

“Apparently, the other combustible materials were too close, and a large quantity of material ignited, and exploded,” the officer wrote.

Efforts to reach the boys’ families were unsuccessful. Their names were redacted from the police report and Harborview Medical Center did not have records of their admittance.

Property records named the owner of the house where the explosion occurred, but a man who answered the phone at the number connected to the address declined to comment.

Seattle Public Schools said it did not believe the boys were enrolled in a Seattle school.

However, it doesn’t appear the boys face criminal charges for their experiment gone awry.

“I don’t think there’s any mystery,” said police spokesman Mark Jamieson. “Kids were messing around with something they shouldn’t have. It went off and there were some injuries.”

Seattle Times news researcher Miyoko Wolf contributed to this report.

Christine Clarridge can be reached at cclarridge@seattletimes.com or 206-464-8983.