Are Hjorungnes, a visiting engineering professor from Norway, was relishing physical as well as academic challenges during his stint at the University of Hawaii, a colleague said.

"He’s a nice guy, a smart guy and athletically very fit," said Tony Kuh, chairman of the UH-Manoa Department of Electrical Engineering.

"He seems to enjoy life, challenging discussions, doing physical things, too — hiking, different things."

Hjorungnes, 40, was last seen Saturday morning at about 9:45 a.m. on a mountain trail run in the hills above Mokuleia with members of an Oahu running club.

The Honolulu Fire Department called off its search yesterday afternoon, said fire Capt. Terry Seelig. Fire Department protocol is to conduct such searches for three days, he said.

Fire and police personnel used search dogs and helicopters during their three-day search, with rescue specialists being lowered by rope into ravines obscured by tree canopies, Seelig said.

"There are no signs of Are or where he went," he said after yesterday’s unsuccessful search by firefighters, police officers and a group of runners.

Hjorungnes is 5 feet 11 inches tall and weighs 150 pounds, with brown hair and brown eyes. He was wearing a white T-shirt, blue running shorts and black running shoes, police said.

He is single and from Trondheim, a town in northern Norway.

Nina Fasi, honorary consul of Norway in Honolulu, said she has been contacted by Hjorungnes’ friends as well as Norwegian newspapers, TV stations and magazines. The Norwegian media have been publishing stories about his disappearance, she said.

"His childhood friend said he is very responsible and in good shape and into sports and athletics," Fasi said.

She said she informed officials at the University of Oslo, where Hjorungnes is a professor of mathematics and natural sciences, of the news. They, in turn, notified his family.

He was among a group of about eight people who took part in a trail run Saturday morning organized by HURT Hawaii (Hawaiian Ultra Running Team).

The run started in the Peacock Flats area behind Dillingham Airfield. The network of trails includes jeep and hiking trails as well as pig trails.

Cheryl Loomis, an ultra runner with HURT, took part in Saturday’s run. She said the group took a water break near the top of the ridge. Hjorungnes and another man, who were faster runners, "took off in front of us, and he took a wrong turn," she said.

Peacock Flats is a 15-mile run with "intense" ups and downs, said Mike Minch, who helped organize HURT members to search for Hjorungnes. The first section, the Kealia Trail, is a switchback trail with an elevation gain of 800 feet. A jeep road climbs another 1,200 feet, he said. Minch, who was not on Saturday’s run, said the group stopped for water at about the 2,200-foot level, after which the trail is mostly downhill.

"He probably took a wrong turn," Minch said. "Once he took that wrong turn, he was in a hurry to get to the bottom," he said.

When Hjorungnes didn’t meet up at the bottom with the rest of the group, club members went back up not more than 30 minutes later but found no sign of him, Minch said.

At Peacock Flats "you can actually walk along an animal trail and not realize it’s not a human trail," Minch said. "You can go on a pig trail for a long way until it ends, and you realize you’re out on a ridge somewhere."

Hjorungnes has been in Hawaii for 10 months to conduct research with the UH-Manoa engineering faculty. Kuh said Hjorungnes’ research involves signal processing.