By Dan Whitcomb
LOS ANGELES (Reuters) - Authorities combed Yosemite National Park in California on Monday for a 22-year-old college student who disappeared after walking away from the rest of his group during a weekend trip into back-country areas of the park.
John Paul Chaufan Field, a senior at the University of California at Santa Cruz, was last seen at mid-morning on Saturday at a campsite near Kibbie Lake in the park's Hetch Hetchy area, Yosemite spokesman Scott Gediman said.
Chaufan Field had hiked there with a group of about 10 other students on Friday, but walked away alone after breakfast on Saturday and was still gone when the rest of the students set off for day hikes, Gediman said.
When he was still missing early the next morning, several students hiked out to contact park rangers, Gediman said.
"Yesterday, we did more of a hasty search and when he wasn't found the decision was made to ramp it up with helicopters and more search teams," Gediman said, adding that about 50 people were now combing the park for Chaufan Field.
"Now it's a full scale, multi-agency ground search," he said.
Gediman said it wasn't clear if Chaufan Field was carrying food or water when he left the Kibbie Lake campsite or where he may have been headed in the nearly 1,200-square-mile (3,100-square-kilometre) park.
His backpack and other gear were left at the camp.
Gediman said there was no sign of foul play, and Chaufan Field wasn't believed to be upset or ill when he left.
He said rangers were still questioning other members of the group for clues to the missing student's whereabouts.
Chaufan Field was described as 5-feet, 5-inches tall with black hair and black eyes, wearing an earth-colored plaid shirt, denim shorts and Vibram FiveFingers shoes.
(Reporting by Dan Whitcomb; Editing by Cynthia Johnston and Eric Beech)