YOSEMITE NATIONAL PARK, Calif. (KRON) — The Washburn Fire burning in Yosemite National Park was caused by humans, park officials revealed at a town hall meeting with residents.

Firefighters were first alerted about the Washburn Fire on Thursday by visitors who spotted smoke as they were walking in Mariposa Grove, the park’s largest grove of iconic sequoias.

“As you all know, there was no lightning on that day. So it’s a human-start fire. It’s under investigation, that’s all I can really say right now. We are looking at that real, real hard,” Park Superintendent Cicely Muldoon told residents who packed Monday night’s meeting in Oakhurst, Calif.

As of Tuesday afternoon, the wildfire had scorched more than 3,300 acres and was 25% contained. More than 500 firefighters are battling the blaze.

The wildfire, dubbed the “Washburn Fire” because of its origins near the Washburn Trail, forced campers and residents to be evacuated.

The Washburn Fire burns on a hillside in Yosemite National Park, Calif., on Saturday, July 9, 2022. (Stephen Lam /San Francisco Chronicle via AP)

Residents living in the community of Wawona were ordered to leave on Friday. About 700 visitors who were staying at the Wawona campground in tents, cabins and a historic hotel were also ordered to evacuate.

The rest of Yosemite National Park remains open this week, however, heavy smoke is obscuring scenic vistas and creating unhealthy air quality for outdoor recreation.

The fire is threatening more than 500 giant sequoias in Mariposa Grove. So far there are no reports of severe damage to any named trees, including the 3,000-year-old Grizzly Giant. “Most of these trees are over 2,000 years old and have experienced fire many times throughout their lives,” Yosemite park officials noted.

TOPSHOT – A large plume from the Washburn Fire rises over Mariposa Grove in Yosemite National Park, California, July 11, 2022. (Photo by NIC COURY / AFP via Getty Images)

Matt Ahearn, an operations section chief with California Interagency Incident Management Team, told concerned residents that the blaze is not spreading rapidly, but it is creating “extreme heat.”

A tree branch was launched into the air from a powerful updraft produced by the fire on Saturday. As the branch dropped back down, it narrowly missed striking two firefighting aircraft. “Fortunately, there were no injuries and no damage,” park officials stated.

Park officials wrote on Tuesday, “The combination of continued warm and dry weather conditions along with the heavy accumulation of large fuels is creating the perfect recipe for the very active fire behavior we are seeing. Observers from a distance should expect to see heavy smoke production for the next few days as the fire activity increases each afternoon. While sections of the fire are not able to be fought head-on by fire crews due to the safety risk for firefighters, much of the rest of the fire is being successfully suppressed, fire lines are being strengthened, unburned fuel in the path of the fire are being burned to ‘starve the fire,’ and hot spots are being cooled.”

The Wawona Road (Highway 41) is closed from the South Entrance to Henness Ridge Road.  Yosemite West remains accessible from the northern side of the Wawona Road. Visitors can use Highways 140 or 120 to enter the park.

Thick smoke from the Washburn Fire is seen on Monday, July 11, 2022. (AP Photo / Godofredo A. Vásquez)
A plane drops fire retardant on the Washburn Fire in Yosemite National Park on July 11, 2022.  (Photo by NIC COURY /AFP via Getty Images)

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– The Associated Press contributed to this report.