PORTLAND, Ore. -- Police and volunteers are searching for a 27-year-old Gresham man last seen at a Larch Mountain campground on Saturday.

Search crews found his coat in the water along the East Fork of the Lewis River on Tuesday.

Vadim Mukhin was camping with friends at the Sunset Falls campground, according to the Clark County Sheriff's Office.

Map: Larch Mountain

According to the sheriff's office, Mukhin and several friends gathered at the Sunset Falls campground to go off-roading in the nearby hills. After a day of that, they went back to the campground for a break. Around 6 p.m., they all went back out again, except for Mukhin who stayed behind. That was apparently the last time he was seen.

Some told the sheriff's department Mukhin had been drinking heavily. The camp site is along the East Fork of the Lewis River.

“As you can see there's a lot of areas where you can't really safely get down to the edge of the river to check,” said Clark County Sheriff's spokesman Sgt. Fred Neiman.

The sheriff's department launched its drone to help check the river and its banks.

“We also have volunteer kayakers who kayak this area regularly,” said Sgt. Neiman.

Extended family members said Mukhin was reuniting with friends after being gone the past four months on a church based mission trip to Panama. His church is called “God Will Provide.”

Mukhin's sister, Tonya, said it's not like him to "just disappear."

“He's constantly in touch with the family, checking in with us,” she said, adding that the family is grateful to the volunteers searching for him. "We appreciate anybody's help.”

Anyone with information is asked to call 911.

KGW's Pat Dooris contributed to this story.