(CNN) -- A brown bear and her cub mauled a group of teenage boys deep in the Alaskan wilderness, forcing rescuers to scramble early Sunday to help the injured.

Two of the teens, participating in a survival skills course, suffered life-threatening injuries, Alaska State Troopers said in a press release, and two had injuries that were labeled "serious, but non-life-threatening." Megan Peters, a spokeswoman for the state police, said those four are in critical condition, while three others had minor injuries or exposure-related issues.

The National Outdoor Leadership School -- whose program the boys were participating in -- claimed in a statement that four people were hurt in the attack.

The mauling occurred around 8:30 p.m. Saturday as the teenagers were crossing a creek in a remote area about 45 miles northeast of Talkeetna. There were no instructors with the group, which was on the 24th of a 30-day backpacking course to learn about teamwork and wilderness-related skills, according to the Wyoming-based program.

The teens told state troopers that they were crossing the river in a line when the bears attacked. Those in front got the worst of the assault.

"They were mauled, very severely," said Peters. "It was truly an emergency situation."

Between ages 16 to 18 and from all around the country, the boys said that they followed protocol in calling out to warn the bears and carrying bear spray, according to the wilderness program.

Afterward, the group set up a camp, provided first aid and activated a personal locator beacon, which is used to alert authorities about one's whereabouts in an emergency.

A helicopter was then dispatched, tracking the beacon's signal and finding the teens in a tent around 2:45 a.m. Sunday, said state troopers.

The rescuers then determined that two of the victims were too hurt to be safely transported by the helicopter for medical aid. A state trooper stayed on the scene, helping tend to those two as well as a third boy who was in the best condition, while the others were flown out for treatment at Mat-Su Regional Hospital in Palmer.

Four hours later, around 6:45 a.m., a better-equipped aircraft arrived to fly out the most seriously injured to Providence Alaska Medical Center in Anchorage, about 150 miles to the south.

A state trooper on Sunday flew around the area, trying to locate the animals responsible for the attack. Peters said Sunday night that "we have not laid eyes on the bear and the cub."

Seven other National Outdoor Leadership School students, as well as three instructors, had been in the Alaska wilderness at the time of the attack and were unaware of the mauling, the state police said. The outdoor leadership school said these 10 people have since been located and "are in the process of being evacuated by helicopter."

In mid-July, wildlife officials in Colorado said they killed a black bear who they believed had wandered into a heavily populated campsite and attacked a teenage boy. The teen fought off the bear, then chased it away after being bit in the leg.

A man was killed weeks earlier in a grizzly bear attack in Wyoming's Yellowstone Park. But park officials said the man, who was hiking with his wife, surprised the female grizzly while she was with her cubs. They determined that the bear was acting defensively and decided not to put the bear down.