Interior Secretary Ryan Zinke (center) with U.S. Rep. Tom McClintock at the Ferguson Fire camp July 21, 2018/HO

A wildfire burning not far from Yosemite National Park's western border was pumping smoke into the park Saturday, and prompting an increase in visitation to Sequoia and Kings canyon national parks.

The Ferguson Fire, which was spotted July 13 and has spread to more than 27,000 acres, was being battled by nearly 3,000 firefighters, whose jobs were made difficult and dangerous by the steep, rugged, hard-to-access terrain. One firefighter died a week ago when the bulldozer he was operating rolled over on top of him.

On Saturday, Interior Secretary Ryan Zinke visited the fire lines with U.S. Rep. Tom McClintock to check on the firefighters' progress.

Thirty-eight helicopters were assigned to fight the flames. Ground crews were working Saturday on building a fire break from El Portal southeast to the Wawona Road, and much of the line was complete and lined with hose lays in preparation for tactical firing operations, according to a release.

Not long after the secretary's visit, Sierra National Forest officials instituted a closure order for a large part of the forest to keep the public both out of harm and out of the firefighters' way.

"Closure of the fire area is necessary to help ensure that no one is injured within or near the active fire perimeter," wrote forest Supervisor Dean Gould. "All National Forest System roads and trails within closure area will be closed due to fire suppression and rehabilitation activities that create a hazard to the public...."

Gould said the closure would remain in place "until the fire is declared out." As of Saturday afternoon, just 7 percent of the blaze was contained.

At Yosemite, officials were warning visitors to be prepared for smoky conditions.

"Visitors to Yosemite should expect poor air quality and limited visibility due to the Ferguson Fire," a notice on the park's website said. "Smoke may be heavy at times, and visitors should be prepared to limit any heavy outdoor activity during the periods of poor air quality."

Park staff added that "some services may be reduced or not be available as a result of smoky conditions or lack of staffing caused by the Ferguson Fire."

The Half Dome web cam in Yosemite National Park on Saturday afternoon showed smoky conditions/NPS

Meanwhile, to the south of the park and the fire officials at Sequoia and Kings Canyon national parks said those two parks were experiencing increased visitation due to fire activity near Yosemite. 

Campgrounds and lodging in the two parks have been full, and visitors were being urged to check for campground reservations at  www.recreation.gov and for lodging information at www.visitsequoia.com.

Visitors can expect to see residual smoke from the Ferguson Fire in the Sierra National Forest north of the parks as well as the recently ignited Horse Creek Fire in the Mineral King area of the parks, which was lightening caused, a release from Sequoia and Kings Canyon said.

Air quality could be unhealthy at times for sensitive groups in the middle elevations of the parks, including Lodgepole, Grant Grove, Cedar Grove, and Mineral King. For air quality information visit go.nps.gov/sekiair.