Nearly two dozen mountaineers and park rangers are searching for the son of Hall of Fame boxing promoter Bob Arum, who’s been missing since a weekend camping trip in the Cascade Mountains of Washington state.

John Arum was expected to arrive home Sunday after climbing Storm King, a rugged mountain peak about a seven-hour drive from Seattle. Family members grew worried when the 49-year-old environmental lawyer and accomplished hiker did not return.

North Cascades National Park spokeswoman Kerry Olson said that John Arum was reported missing Monday, and is thought to be by himself in the area around the mountain. So far, two days of searching—including aerial sweeps of the region — have not brought up any clues.

“He’s a very experienced climber and hiker, and familiar with the territory,” Olson said, adding that Arum had already summited a peak near the one he went missing on.

John Arum has been on a quest to climb the 100 highest summits in Washington.

Family members told The Associated Press on Wednesday that rangers had found his campsite, but there were indications that John Arum had not been there since Saturday.

“We’re keeping our fingers crossed,” said Bob Arum’s son-in-law, Todd duBoef. “The last I talked to Bob, they were sending a helicopter up, but the area where he’s missing, there’s so much timber that it’s hard to see anything. We’re just waiting to hear something.”

Bob Arum learned Tuesday that his eldest son was missing while in Los Angeles, at the start of a three-city media tour to promote Manny Pacquiao’s next fight against Antonio Margarito. He left for Seattle that afternoon and connected with park rangers orchestrating the search.

DuBoef took over the rest of the media tour, with stops in New York on Wednesday and Dallas on Thursday. The fight is scheduled for Nov. 13 at Cowboys Stadium in Arlington, Texas.

“We miss him for this press conference and we feel bad with what happened to his son, and I pray for him,” Pacquiao said Wednesday. “It’s pretty quiet without Bob.”

DuBoef said park rangers had been searching on foot for John Arum but had found no trace of him other than his campsite. Arum faced at least one day of adverse weather, and fog and rain had hampered efforts to cover the terrain by air.

“The terrain in the North Cascades is difficult. These mountains are steep,” Olson said. “He had experience, but certainly there’s a risk involved with mountaineering.”

Storm King, the area in the Cascades where John Arum went missing, rises more than 8,500 feet above sea level. There are several hiking trails around the mountain, including a well-known loose rock route on the south face, and it stands in the background of Lake Chelan.

Family members said that John Arum had 18 peaks remaining to reach his goal of climbing the 100 highest in Washington State. Storm King is ranked No. 51.