Rescue workers in Wyoming are continuing their search for James “Randy” Udall, brother of Sen. Mark Udall, D-Colo., who has been missing since last week after failing to return home from a solo hiking trip.

The 61-year-old, who is also the cousin of New Mexico Democratic Sen. Tom Udall, is an experienced backpacker, according to multiple local media accounts. The search, which began on June 28, is being conducted over a 225-mile area in the Wind River Range by more than 30 workers from several agencies, according to KMGH TV in Denver.

“Thank you all for prayers & kind words about my brother. I know USFS & WY officials are doing everything they can to find Randy,” Mark Udall tweeted Tuesday.

Randy Udall is an environmentalist and alternative energy advocate in addition to being the younger brother of Colorado’s senior senator and the son of the late longtime Arizona congressman Morris Udall. According to the Denver Post, he had hiked the trail where he was last seen multiple times over the past 30 years.

On Tuesday, the Colorado senator’s colleagues sent well wishes to the Udall family as the search continued.