The heart of Yosemite National Park in California, shut down for nearly three weeks due to a deadly wildfire, was reopened to visitors on Tuesday, but smoke limited visibility 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 around the park's northwestern corner, but fire crews have carved containment lines around 86 percent of its perimeter.