Zion National Park, Utah

A member of a search and rescue team wades in to Virgin River during a search for the hikers Wednesday, Sept. 16, in Zion National Park, Utah. Rick Bowmer / AP

"Our condolences go out to the family and friends of the canyoneers, " Zion National Park Superintendent eff Bradybaugh said in a statement.

Dozens of search and rescue workers spent hundreds of hours scouring the canyon, the National Park Service said. Rain and continuing flooding hampered the initial effort to find the hikers, but conditions improved by Thursday, it said.

One of the victims was identified by the Ventura County, California, sheriff's office as Sgt. Steve Arthur, a 21-year veteran of department. The sheriff's office said that Arthur had been hiking with his wife, Linda, who was also caught in the flooding.

Authorities have not identified the remaining victims.

Around 300 search and rescue workers were looking f or Tyson Lucas Black, who turned 6 years old in August, officials said.

Rachel Carnahan, a volunteer spokeswoman with the search effort, told NBC News that searchers were focusing on a seven-mile stretch on the edge of Hildale.

"They're continuing to go back over the same areas, " she said.

Residents watch rescuers search along the Short Creek after a flash flood in Hildale, Utah September 15, 2015. DAVID BECKER / Reuters