THOUSAND OAKS, Calif. (AP) — The Latest on the deadly explosion of a homemade model rocket in California (all times local):

3:50 p.m.

Authorities say two Southern California high school students attached a homemade model rocket to a skateboard before it exploded and killed one of the teens.

The blast Monday in the courtyard of a Ventura County elementary school killed 18-year-old Bernard Moon of Thousand Oaks. His 17-year-old friend was injured and is in stable condition.

Sheriff's Detective Timothy Loman said Tuesday that the teens built the rocket and attached it to the skateboard as a propulsion device. Other details are under investigation.

Authorities say the experiment wasn't sanctioned by the school.

The teens attended Thousand Oaks High School, which said in a Twitter post: "Our hearts are broken."

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10:45 a.m.

Investigators will try to piece together a homemade model rocket that exploded at a Southern California school, killing a high school student and sending his friend to the hospital with minor injuries.

Ventura County sheriff's Capt. Garo Kuredjian says the two high school seniors apparently were experimenting with "some sort of chemical combination" before the accidental blast Monday evening in the courtyard of their neighborhood elementary school.

Kuredjian said Tuesday that the fuel wasn't propane, as officials initially reported.

Investigators will try to determine the size and shape of the rocket, which blew apart.

He says the experiment wasn't sanctioned by Madrona Elementary and the high-schoolers likely were using the courtyard because it's an open space.

The victims weren't immediately identified, but school district officials said they're seniors at nearby Thousand Oaks High.

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1:50 a.m.

Authorities say a young man has died and another was injured after a model rocket exploded at a Southern California school.

Ventura County Sheriff's authorities said late Monday the 18-year-old man suffered critical injuries and died at a hospital. A juvenile was also taken to the hospital with minor injuries.

County fire officials said the explosion was reported around 7:30 p.m., after class was let out at the school in Thousand Oaks.

Fire Capt. Mike Lindbery said the two apparently were using a small propane cylinder to make a model rocket and the cylinder exploded in someone's hands.