A beloved Palo Alto dentist has gone missing in the Wyoming wilderness after he became separated from his hiking group over the weekend, the Fremont County Sheriff's Office and his niece said.

Steve Keller, 76, was reported missing on Saturday, Sept. 2 at around 4:30 p.m. in the Wind River mountains near Lander, Wyoming, according to the Wyoming online media site Buckrail.

Keller was hiking near Steamboat Lake in a remote area of the Wind River Reservation. Keller left Steamboat Lake, where his group was camping, for a day hike without a pack, according to a police missing persons flier.

Search and rescue teams are looking for Keller but weather conditions have caused delays.

"We are deeply concerned," Keller's niece, Betsy Briggs Miller, said in a Facebook post, asking the public to share the information if they know anyone in or near the Wind River or Lander area.

Keller, who is retired, worked with the Palo Alto Dental Group starting in 1979. He attended Georgetown University School of Dentistry on a scholarship from the United States Navy and served as a naval officer and general dentist at Naval Air Station Moffett Field in Mountain View for three years, according to the dental group's website. He became a full partner in 1982.

"He is proficient in all aspects of general dentistry, and seeks simple solutions to complex problems. He values his relationships with patients, and always schedules enough time to explain procedures and provide thorough treatment," his website bio stated.

Keller is described as a white male who was wearing a green jacket, a black, blue and green Patagonia fleece and is 6 feet tall and weighs 170 pounds.

This story will be updated as more information becomes available.