IRVINE, Calif. - In the search for a college student lost while hiking in Orange County's backcountry, things were beginning to look grim.

It had been four days since she went missing. Steep ravines with 10-foot-high brush hindered rescue efforts and thwarted helicopters with infrared cameras. When searchers found her companion dehydrated and exhausted, he said they'd become separated and he hadn't seen her recently.

But on Thursday, Kyndall Jack's voice secured her rescue. The 18-year-old's screams from a cliff in the Trabuco Canyon area caught the attention of a search team and led to a protracted and dramatic rescue.

"I yelled out to her to see if she could see me," said rescuer Mike Leum. "She said she could see me, but I could not see her."

Leum shouted at her to wave her arms. She could only wave one, she told him. The other was hurt.

Leum finally spotted Jack on a rocky hillside. He kept his eyes on her as he directed a helicopter to hoist her away.

"She was severely dehydrated," he said. "She was confused - she didn't really know much of anything."

Jack, a college student from Costa Mesa, Calif., was airlifted to the University of California, Irvine Medical Center, where a spokesman said she was undergoing tests and being treated for dehydration and hypothermia. Her family "would like to thank everyone for their help and to thank them for keeping her in their thoughts and prayers," a hospital spokesperson said.

Her friend and hiking companion, Nicolas Cendoya, 19, rescued Wednesday night, remained hospitalized with dehydration and superficial cuts.

Although officials said they were thrilled that the hikers had been rescued, they used the opportunity to remind the public of the hazards that inexperienced and unprepared hikers pose to themselves and rescuers.

That danger was driven home in the final rescue push when a reserve sheriff's deputy plunged 60 feet down a hillside while trying to reach Jack. The volunteer deputy, who was not identified, sustained a serious head injury and was being treated in the intensive care unit of Mission Hospital Regional Medical Center in Mission Viejo, officials said. His injuries were not considered life threatening, they said.

The massive search operation, which began Sunday night, grew to include 16 different state and local agencies. Asked at a news conference about the cost of the search, Orange County Sheriff's Lt. Jason Park said he didn't know, "but it's a good question."

"We're not in a position to point fingers and to claim who's to blame here," Park said. "I have no doubt they came out here with the best of intentions ... this is a complicated environment and before you know it, you're lost."

Jack and Cendoya, friends from Costa Mesa High School, set out for their hike Easter Sunday. Both were accomplished athletes who regularly worked out together at a local gym, but according to one friend, they were not experienced hikers. They took no food, did not inform friends of their route and Cendoya was dressed in board shorts and a T-shirt.

After embarking on a popular trail leading to a waterfall, they apparently strayed from the path and quickly became lost in the rugged terrain and thorny chaparral. As night fell, Cendoya used the remaining power on his dying cellphone to call 911.

"He was panting and said, 'We're out of water,'" Orange County Fire Authority Capt. Jon Muir said. Cendoya estimated that he and Jack were about a mile from their car in Holy Jim Canyon. The distance proved right, but the location he gave the operator was "totally" wrong, Muir said.

After four days searching by helicopter, on foot, on horseback and with bloodhounds, hikers spotted Cendoya just before 8 p.m. Wednesday, wedged in a crevice high above a creek bed, surrounded by brush.

He was 500 feet from a busy roadway, but disoriented from extreme dehydration, authorities said. He had lost his shoes and had cuts and scratches on his feet and body. He told authorities he thought Jack had already been rescued.

Just before noon the next day, a team of sheriff's deputies from Los Angeles and Ventura counties heard a woman's screams. They summoned additional rescuers and a helicopter, which eventually located Jack under a canopy of brush high on a hillside.

She was roughly 1,400 feet from where Cendoya had been found and less than a mile from their vehicle.

It took the helicopter rescue team about 90 minutes to lift her off the hill in a harness. It was during this period that the reserve deputy, trying to approach her on foot was injured.

Park noted that the searchers who rescued Cendoya had to cut through the brush to get to him and couldn't actually see him until they were about 10 feet away.

Cendoya told hospital staff he covered himself with brush at night for warmth, and he prayed.

Dr. Michael Ritter said Thursday that Cendoya would remain in the hospital for a few days and that the rescued hiker was hoping his ordeal would convince others to be better prepared.

"He is very concerned that we offer pointers to all the hikers out there so that they can take care," the doctor said.

(Times staff writers Harriet Ryan in Los Angeles and Jill Cowan and Anh Do in Orange County contributed to this report.)

• Read more articles by KATE MATHER, RICK ROJAS AND IRFAN KHAN

Order Reprint