OROVILLE, Calif. -

Butte County Search and Rescue conducted a full scale search Sunday for an at-risk missing Oroville man missing since Saturday afternoon.

81-year-old John Chesley was reported missing around 1 o'clock p.m. Saturday in the Park View Drive and Viewcrest Drive area, close to his home.

He's known to have dementia and is hard of hearing, complicating search efforts.

A helicopter scoured the foothills east of Oroville off Old Olive Highway while Butte County Search and Rescue ATVs, foot patrols and search dogs hit the ground.

A spokesman with Search and Rescue said terrain in the area crews are searching is making their job tough.

"The terrain is making us work really hard on this, on top of the canopy and tree cover," says Butte County Search and Rescue's Kevin Lucero. "Based on the information I have he's possibly mobile. Folks that may be along some highways--162, Old Olive Highway area--if he walked down towards that area, it's very likely that he may have been picked up and given a ride some place."

The search for Chesley was suspended around 4 p.m. Sunday so crews could regroup and rest.

Lucero says they haven't found any clues and plan to expand the search area when they continue the search again around daybreak Monday.

If you believe you may have information about Chesley's whereabouts you're asked to contact the Butte County Sheriff's Office.