UPDATED 10:00 p.m.

The

is continuing a two-day search for a missing

volunteer last seen near Riddle High School.

Mark Bosworth, 54, of Portland, was reportedly last seen Friday night leaving a booth on Main Street in Riddle after 11 p.m., according to the sheriff’s office. The town, south of Roseburg, was the sixth stop on the annual seven-day cycling tour, which ended Saturday.

Bosworth, a principal GIS analyst at Metro, has been a dependable volunteer with Cycle Oregon for the last four years, said Jerry Norquist, Cycle Oregon ride director.

"We're obviously very concerned and doing our best to find him," Norquist said Sunday. "The community (of Riddle) is really stepping up."

A search and rescue team, including three K-9 units and three four-by-four vehicles and firefighters, is combing a four-mile radius in Riddle, said Deputy Sheriff Brian Melvin. The team passed out 400

and went door-to-door to Riddle residents, asking for help in the search. A marine patrol also floated Cow Creek, and search efforts were to continue Sunday until dark, Melvin said.

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Authorities pursued leads Sunday from residents and event participants, who said they saw a man matching Bosworth’s description hitchhiking east out of Riddle on Yokum Road late Friday or early Saturday morning. The two-lane road hugs Cow Creek and the Umpqua River before meeting up with Interstate 5 at Exit 101.

But a search along the road turned up no signs of Bosworth.

“Nothing has popped up,” Melvin said. “We’re just basically trying to cover area in hopes that he’s somewhere close by.”

Norquist, who stayed behind in Riddle, said the situation is unusual for Bosworth, who often showed up early to the bike group's meetings.

Bosworth's wife, Julie Bosworth, and their two daughters are expected to be at the scene today to show their support, he added.

Bosworth recently battled lymphoma, but the disease was thought to be in remission, Melvin said. He had visited a doctor in May and received a clean bill of health, his family told authorities.

“Physicians say he was healthy as an ox,” Melvin said. But authorities had not ruled out the lymphoma had returned and caused unpredictable behavior.

Sheriff’s deputies first responded Saturday afternoon and after interviewing witnesses, found no signs of foul play. A preliminary investigation showed Bosworth may have been suffering from a medical condition before he disappeared, according to a news release.

Follow daily updates from The Oregonian's John Killen and Allan Brettman on their Tumblr blog,

Several K-9s and a search and rescue team of about 40 people, including Cycle Oregon volunteers and firefighters, looked for Bosworth Saturday in the streets near the high school and Main Street.

After combing neighborhoods within three miles of the Umpqua River until dark, the team called off the search to continue again Sunday morning.

The sheriff’s office described Bosworth as 6 feet tall, about 180 pounds, with gray hair and blue eyes. He was reportedly wearing a gray hoodie sweatshirt, black bicycle pants and a hat.

Anyone with information is asked to call the sheriff’s office at 541-440-4450.

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