Two climbers have fallen to their deaths while climbing the rock face known as "El Capitan" in California's Yosemite National Park.
Jason Wells, 46, and Tim Klien, 42, died trying to scale the 900m-tall granite formation using the Free Blast route on Saturday morning.
National Park Rangers received multiple 911 calls about the fall at around 8.15am but neither climber survived.
No further details have been released about how Mr Wells, from Boulder, Colorado, and Mr Klien, of Palmdale, California, lost their lives.
They were reportedly training for a speed ascent of the rock formation with the simul (simultaneous) climbing method.
The accident follows the death of a hiker who slipped while climbing the granite cliffs of Half Dome in Yosemite last week.
British climber Andrew Foster, 32, was killed at El Capitan last September when he was crushed by falling rocks in front of his wife Lucy.
There are more than 100 accidents in the park every year, most of them involving experienced climbers, according to the National Park Service.
"At least 80 per cent of the fatalities and many injuries, were easily preventable," wrote Yosemite Ranger John Dill in his guide Staying Alive.
"In case after case, ignorance, a casual attitude, and/or some form of distraction proved to be the most dangerous aspects of the sport."
El Capitan, which translates as "The Captain" or "The Chief", is one of the best-known landmarks in the national park and is considered a world-class challenge for rock climbers.
The Free Blast route involves the first 10 pitches, or stops, of El Capitan's Salathe Wall, one of the original technical climbing routes.
