Calif. Teen Hikers Missing: Search intensifies for Nicholas Cendoya and Kyndall Jack in Cleveland National Forest

(CBS/AP) RANCHO SANTA MARGARITA, Calif. - The search for two missing California teens who vanished while hiking in Orange County's Cleveland National Forest grows more urgent with every hour since they were last heard from on Sunday night.

PICTURES: Calif. teen hikers missing

Parents of 19-year-old Nicholas Cendoya and 18-year-old Kyndall Jack hoped for a sign of their kids somewhere in the wooded area as experts and volunteers continued the hunt Wednesday morning, sheriff's Lt. Erin Guidice said.

Searchers were concentrating on an area of the Holy Jim Trail where a bloodhound picked up a scent during an overnight search, Guidice said.

The teens called authorities Sunday night saying they were lost about a mile from their car in Holy Jim Canyon, but their cellphone lost power soon afterward.

Friends who joined the search told CBS Los Angeles that the couple is very active.

"They're very fitness-oriented, so it's not really a shocker that they'd be hiking but it's a shocker that they'd be missing because of it," Daniela Conderes told the station.

The rocky, tree-shaded dirt trail leads to a waterfall on a 2.8-mile round trip and is popular with day hikers. Its difficulty is listed as moderate to serious on a U.S. Forest Service website. However, the lost hikers "did not keep to the trail," Guidice said.

The area has heavy brush and a creek running through it, she said. Temperatures were moderate Friday, following an overnight low in the 50s.

The area is in a section of the national forest in the Santa Ana Mountains, which lie along the border of Orange and Riverside counties southeast of Los Angeles. The trail ranges in elevation from about 2,000 feet to about 4,000 feet.

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April 2, 2013 - Calif. Teen Hikers Missing: Authorities resume search for Nicholas Cendoya and Kyndall Jack in Cleveland National Forest