Searchers on Tuesday entered their fourth day searching for the wife of Randy Merrell, who helped found the Merrell Boot Co., in a remote area at the bottom of the Grand Canyon.

Lou-Ann Merrell and Jackson Standefer, her 14-year-old stepson, were last seen trying to cross Tapeats Creek in Grand Canyon National Park on Saturday but lost their footing to slipped into the water. The pair were hiking below canyon’s North Rim with Randy Merrell and Jackson Standefer’s mom, Julie Standefer.

The search includes three ground teams consisting of about 20 people total, a National Park Service helicopter, a drone and an inflatable motor raft that was flown into the canyon.

Family members said that rescue teams discovered the pair’s backpacks with their belongings still inside. While that means the pair won’t have any food or supplies, search teams say there were indications that they had been able to take their backpacks off after they fell into the river.

Standefer’s uncle Mark McOmie told the Denver Post that both Lou-Ann and her husband Randy Merrell are experienced hikers and know the area well. McOmie said. ‘If they can get to a spot where they cannot be in the water and stay warm, she’s got the skills needed to get them through it. The odds aren’t great. But given their skills and knowledge of the area, that will probably lead to the best possible outcome.’

An updated statement released Tuesday evening by the family of Jackson Standefer reveals that the Merrell shoe company had been working over the past several hours to provide climbers and rescuers to continue the search. The statement read in part, “The search for Jackson and LouAnn continues, and the overwhelming support has helped us remain positive throughout this process.”

Randy Merrell, along with Clark Matis and John Schweizer, founded Merrell Boots in 1981. Randy Merrell sold his shares in 1986 in a shift to focus back on making custom boots and teaching bootmaking. He founded a small custom-built shoe firm, Merrell Foot Labs, in Vernal, UT. Merrell Boots was then sold to Karhu in 1987 and eventually to Wolverine Worldwide in 1997.

Photo courtesy Merrell