The search continued on Thursday for a female hiker who went missing over the weekend in Orange County's Cleveland National Forest, hours after her hiking companion was found confused and dehydrated near where the pair had parked their car.

Orange County Sheriff's officials have mounted a massive search involving multiple law enforcement agencies by air and ground for Kyndall Jack, 18, who along with her partner, Nicholas Cendoya, went missing on Easter Sunday.

Cendoya was found by a hiker about a half-mile from where he and Jack parked their car at 9 p.m. on Wednesday, said Orange County sheriff's Lt. Jason Park.

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He was "severely dehydrated and disoriented" and taken to a hospital where he was listed in serious condition.

Park said searchers will continue scouring the area near where Cendoya was found as they look for Jack, who, like Cendoya, was described as athletic and in good health.

About 40 rescue workers, some on horseback, searched for Cendoya and Jack on Wednesday, Park said.

Many volunteers joined the search, including two who became lost and had to be tracked down and rescued.

Fearing that novice rescuers could end up interfering with the search, officials have discouraged volunteers from joining in.

Cendoya and Jack, both Costa Mesa residents, called authorities about 8:25 p.m. Sunday to say they had gotten lost while hiking in Holy Jim Canyon in the Cleveland National Forest, said Gail Krause, an Orange County sheriff's spokeswoman, adding that their cell phone's battery then wore down.

Authorities could not get an accurate GPS "ping" from the phone to pinpoint the hikers' location, said Sheriff's Lt. Erin Giudice.

City News Service contributed to this report.