LOS ANGELES (Reuters) - The heart of Yosemite National Park in California, shut down for nearly three weeks due to a deadly wildfire, was reopened to the public on Tuesday, but smoke lingered in the air and a key route to the park’s best known landmarks remained closed.

The reopening of Yosemite Valley, by far the most heavily visited area of the park, came as firefighters continued to make slow, steady progress containing the last hot spots of the Ferguson Fire, which erupted July 13 at the edge of Yosemite.

The blaze, one of the largest of dozens that have burned across California this summer, has charred nearly 97,000 acres in and around the park’s western end, but fire crews have carved containment lines around 86 percent of its perimeter.

The park closure has taken a major toll on the area’s local economy. Some 4.3 million visitors spent an estimated $452 million last year, most of that during the summer.

Two roads into Yosemite Valley and the valley itself were reopened on Tuesday for the first time since July 25. But the north-south entrance route, Highway 41, remained closed, along with a road to the famed Glacier Point overlook and the Merced Grove of giant sequoia trees due to fire in those areas, park spokeswoman Jamie Richards said.

Visitors were cautioned to expect diminished visibility in Yosemite Valley. Richards said a haze of smoke lingered high above the valley on Tuesday but did not impede views of such attractions as Bridalveil Fall and the towering granite monoliths of El Capitan and Half Dome.

At its worst a week or two ago, smoke grew so thick in the valley that “you could not see 20 feet in front of you, like you were in a big fog bank,” Richards told Reuters by phone.

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Park employees reported a surge in wildlife sightings due to the lack of human activity during the closure. “We saw bears walking down the road. We saw bears out playing in the river,” Richards said.

Visitors began trickling back as closures were lifted at 9 a.m. local time, and by midday it was “almost like an average day in August,” with valley parking lots and lodging facilities “fairly packed,” she said.

No major landmarks or structures have been lost inside the park, but the latest valley shutdown was the second longest in Yosemite’s history, eclipsed only by a two-month closure of the entire park in early 1997 due to severe flooding, according to Richards.

Two firefighters were killed last month by the Ferguson fire, one of three fatal California wildfires this season.

The state’s largest-ever fire, raging at the southern end of the Mendocino National Forest since July 27, claimed the life of a firefighter from Utah on Monday, even as containment of the blaze rose to 68 percent. That conflagration has now scorched 354,000-plus acres.

Three other firefighters perished in the devastating Carr Fire, which also killed four civilians and a utility worker and burned more than 1,500 structures. The Carr fire stood at 65 percent containment after blackening 207,000 acres.