Authorities from several agencies are searching for a missing bicyclist on the trails at Lake Grapevine's Murrell Park.
Flower Mound police say 30-year-old Wesley Andrew Hixson, of Roanoke, got separated from his riding partner on the North Shore Trial, he was last seen at 10 a.m. Saturday.
"This trail is so rugged you can be riding with someone and be separated from them because of the windy up and down turns," said Flower Mound Police Capt. Richards Brooks.
Police say Hixson crashed his mountain bike prior to getting separated and may have suffered a head injury and could be disoriented somewhere along the 23-mile bike trail.
"This is rough rugged terrain," said Brooks. "The back trail is densely covered, [there's] a lot of rock and a lot of changes in elevation. It's a difficult area to search."
Hundreds of volunteers and several emergency agencies joined the search, including more than 100 Arlington firefighters. Many of them were off-duty and came to support one of their own. Hixson's father is a veteran firefighter with the department.
"It's emotionally draining and you see it," said Lt. Lee Tovar with the Arlington Fire Department. "But we're here for him, everyone is here for him."
Crews searched through 39 square miles of wet and muddy terrain, while not giving up hope.
"Right now we're searching everywhere," said Tovar. "We''re not leaving any space behind. We don't know what happened. We don't know where he’s at."
Bike patrol officers, boats, the Texas Department of Public Safety helicopter, Flower Mound police and fire personnel as well as Texas Parks and Wildlife life personnel and K9 teams have been searching the area for a day and a half.
Hixson's vehicle, with his cell phone inside, was located at Rockledge Park, according to Flower Mound police.
Hixson was last seen wearing a black t-shirt, black shorts, a black helmet and sunglasses.
Anyone with information on Hixson's whereabouts is asked to call 972-539-0525.
NBC 5's Johnny Archer contributed to this report.