A limb from an oak tree fell on a popular part of Yosemite Valley early Friday, killing two young campers who were sleeping in a tent, according to Yosemite National Park officials.
Park rangers responded to the Upper Pines Campground about 5 a.m., but it was too late, the park service said in a statement.
The names, ages, and places of residence of the victims are not being released. The campers were only described as "minors." "Our thoughts are with the families as they grieve this tragedy," said park Superintendent Don Neubacher.
The area around the oak tree along with the broken branches has been cordoned off with yellow caution tape. "We just suggest people be aware of their surroundings, but in this particular situation, they were in a designated campsite," a park ranger told reporters at the site of the accident.
"What makes me sad is that it was totallly out of the control," a camper at Upper Pines Campground said.
Park officials are currently investigating what caused the limb to break off.
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Falling trees are common in forests, especially during California's drought. "It's probably more common than you think," said Pete Angwin, a pathologist for the U.S. Forest Service Pacific SW region. Angwin wouldn't comment on the Upper Pines Campground case, but confirmed that the Forest Service has seen an uptick in the number of dead and decaying trees. "Some trees just die from a simple lack of water, they also die because they are not able to fight off various insects," he said.
The Forest Service is currently running aerial surveys to keep an eye on tree mortality rates. "Trees that are dead are the most likely to fall," Angwin said. He added that decay in oak trees is fairly common.
On Sunday, a wildland firefighter was killed near Lake Tahoe, battling the Sierra Fire, after a tree fell on him. A second firefighter was treated for injuries during the same incident.
In July 2013, a 21-year-old camp counselor at Camp Tawonga near Yosemite died after a tree fell on her. Three others were injured. In May 2015, legal documents obtained by NBC Bay Area's Investigative Unit showed camp leaders had been warned about the tree for years. Read and watch Vicky Nguyen's investigations below:
- WE INVESTIGATE: Camp May Have Ignored Warnings Before Deadly Accident (May 2015)
- WE INVESTIGATE: Family Protests Death of Camp Tawonga Counselor (May 2015)
In January of 2012, a Yosemite parks concession employee was killed when a branch from a tree fell and struck his tent cabin.
NBC Bay Area's Lisa Fernandez contributed reporting.