KREM-TV, Spokane, Wash.

MOSCOW, Idaho — At least four students were injured after an experimental rocket exploded at the University of Idaho, school officials said early Friday.

The incident occurred in a school parking lot next to a campus steam plant, the University of Idaho said. Emergency personnel took the individuals to Gritman Medical Center, the university confirmed in a statement on Twitter.

Parents of the victims were notified, the University of Idaho confirmed, adding that all victims were "alert" and "communicating" with school personnel. Their identities and injuries were not disclosed. University officials confirmed the students were all out of surgery and in recovery as of Friday morning.

According to campus authorities, several students gathered Thursday night to test an experimental rocket. The students were part of the Northwest Organization of Rocket Engineers, which according to the university's website, is made up of faculty and students who design, build and test rockets. University officials confirmed the students were testing rocket fuel at the time of the incident.

Grant Thurman, a University of Idaho student who was at the scene when the rocket exploded, said the group had tested the rocket last week, but made several changes before they tested it again Thursday night.

"We were testing a new fuel design for the rocket engine and we didn't have reason to believe it would blow up or anything because it was a slow-burning fuel, but as soon as it was lit, it blew up," said Thurman.

At a news conference Friday morning, University of Idaho officials said the experiment was not intended to launch the rocket. University officials said the rocket was 8 inches to 12 inches of galvanized metal pipe.

The University of Idaho said the incident was not a bomb threat. The FBI arrived on the scene, which Moscow police said is routine protocol.

Contributing: Charles Ventura, USA TODAY.