YOSEMITE NATIONAL PARK, CALIF. — A hunk of rock "the size of an apartment building" fell off the granite face of El Capitan in Yosemite National Park on Wednesday, killing one person and injuring another on a mountain at the height of climbing season, officials and witnesses said.



At least 30 climbers were on the wall at the time, but it was not clear if the victims were climbers or tourists, ranger Scott Gediman said.



"It was witnessed by a lot of people," he said.



The injured person was taken to a hospital near the park. No names were immediately released.



El Capitan is one of the world's largest granite monoliths towering 4,000 feet above Yosemite Valley.



Several people made emergency calls, reporting the rock fall from the Waterfall route on the east buttress of El Capitan.



Officials didn't provide details on the size of the rock fall, but climbers posted pictures on social media from hundreds of feet up the wall showing billowing white dust moments after the crash.



"I saw a piece of rock, white granite the size of an apartment building, at least 100 feet by 100 feet, suddenly just come peeling off the wall with no warning," said Canadian climber Peter Zabrok, 57, who was scaling El Capitan and was above the rock fall.



Zabrok said he has climbed El Capitan dozens of times and has "never seen anything like this."



Mountaineers from around the world travel to the park in the Sierra Nevada to scale El Capitan's sheer face. Fall is one of the peak seasons because the days are long and the weather is warm.



Rock falls are common in Yosemite but seldom fatal.



Ken Yager, president and founder of the Yosemite Climbing Association, reviewed photos of the cliff face and debris field, estimating the relatively thin piece that broke off covered an area big enough to fit five houses.



"It cratered and sent stuff mushrooming out in all directions," said Yager, fearing that its victim was someone he knew from the climbing community.



Zabrok said he and friends were in the middle of a six-day climb of the Waterfall route on the right side of El Capitan when they saw it.



"Boy, I don't know how anybody could have survived that," he told KFSN-TV, the ABC affiliate in Fresno.



Peering down from his perch 2,000 feet up on the rock, Zabrok said he saw a rescuer lowered by helicopter and "I believe he grabbed one survivor."



He later saw rescuers moving someone on a litter.



"It was done at tremendous peril to the rescuers because there were three subsequent rockfalls that were all nearly as big and would have killed anybody at the base," he said.



Climber Kevin Jorgeson said he and climbing partner Tommy Caldwell witnessed a massive rock fall in the same area while they prepared for a trek that made them the first people to free-climb the Dawn Wall on El Capitan in 2015.



First they heard a rumble and then they saw a white cloud of dust.



"Yosemite is just a really active, wild place. It's always changing," Jorgeson said. "It doesn't make it any less tragic when someone gets in the way of that."



In 2013, a rock dislodged and severed the rope of a Montana climber who was scaling El Capitan.



Mason Robison, 38, fell about 230 feet to his death. It was Robison's gear digging into the side of the mountain that caused the rock to dislodge.



Yosemite remained open after Wednesday's rock fall, and other activities throughout the park weren't affected, rangers said.