MOSCOW, Idaho -- Four students were taken into surgery after a rocket fuel experiment went awry in a parking lot at the University of Idaho Thursday night.

The explosion happened at 9:52 p.m. local time in a lot next to the Steam Plant on 6th Street, where the students had gathered to test the rocket.

Dan Ewart, VP for Infrastructure at U of I said first responders were on scene within minutes. All four injured students were taken to Gritman Medical Center in Moscow. Three were listed as stable Friday morning, while the fourth was in critical condition, NBC reported.

Ewart could not say Friday whether any of their conditions had improved, but said all of the students were now "alert and communicating."

"What we know right now is that they're out of surgery and recovering," he said.

The students are members of the Northwest Organization of Rocket Engineers, a university-sanctioned group, although it's not clear whether the experiment had been OKed by the university, Ewart said.

"We're conducting a review of this entire process and so we don't have a lot of that information at this time, but again, the safety of our students is opur primary concern, " he said.

The students' names have not been released at their request, but Ewart said three of them are engineering students. At least one of them was wearing protective gear over his or her face when the rocket fuel ignited, Ewart said.

A faculty advisor was present when the explosion happened, he said. That person wasn't hurt.

Authorities have not released whether the students' injuries are burns, shrapnel injuries, or something else.

The device was a galvanized metal pipe, between 8 and 12 inches long and about 1 1/2 inches in diameter that had been filled with rocket fuel. It had been placed on a wooden pallet for the experiment; when it blew up, Ewart said, the blast also destroyed the pallet.

Moscow Police Chief James Fry said city code prevents the launching of any projectiles - including fireworks - without a permit from the city of Moscow. The students performing the experiment did not have a permit, he said.

But Ewart pointed out the students had not planned to launch the device into the air.

"The device that was exploded was actually a test for the rocket fuel itself, it was not intended to be a rocket," he said.

Fry said the incident is not currently being looked at as a criminal investigation. Both the ATF and the FBI are participating in the investigation. Ewart said that is "not uncommon" for local police to contact the FBI in similar situations, because of the larger amount of resources federal agencies have access to.

Ewart said the university is also working to gather more information about what happened, and will release more information as it becomes available.

"Please keep the students in your thoughts as they recover from this incident," he said.