SALEM, Ore. — Much of Oregon was wrapped in a haze of smoke Monday as dozens of wildfires burned in the state, with one blaze forcing part of an interstate highway to be closed.

In the Willamette National Forest alone, 16 fires covering 71 square miles (184 sq. kilometers) were burning, officials said. Campfires were banned and a third of the forest was off limits, the forest service said.

In southwest Oregon, evacuations were ordered in a rural area near Cave Junction because of another fire. The current size of the blaze was unknown because heavy smoke has kept infrared mapping flights grounded, fire managers said.

“Smoke levels are creating unpleasant and unhealthy conditions across much of southwest Oregon,” the Joint Information Center said in a statement.

But smoke also filters sunlight, limiting additional heating of potential fuels on the ground and stifling small fires, the center said.

Air quality alerts were issued for several parts of the state. Doctors recommended that anyone with existing pulmonary conditions such as asthma stay indoors.

On the northern end of the state, a fire in the Columbia River Gorge that separates Oregon from Washington state caused ashes to drift onto the town of Cascade Locks. A stretch of Interstate 84 that runs by the town was closed because of the fire, the Oregon Department of Transportation said Monday evening. The highway will reopen when authorities determine that the road is safe.

Evacuation orders remained in place in and around Cascade Locks for 283 structures, including 15 businesses. After quickly spreading since it started on Saturday, apparently from a youngster playing with fireworks, the fire held the same position overnight and is an estimated 3,200 acres (1,295 hectares).

Native Americans who fish for salmon in the broad Columbia River consider Labor Day their busiest day to sell the smoked fish, but a market where they sell it by the Bridge of the Gods was quiet, Oregon Public Broadcasting reported.

Some hikers on Pacific Crest Trail, which runs through the area, were seen in Cascade Locks and told OPB that fires had prevented them from hiking about half the trail in Oregon.

The fire in southwest Oregon, which has burned more than 219 square miles (567.21 sq. kilometers) was also threatening a tree that marks the site of a bombing of the continental United States by the Japanese during World War II, fire management officials said.

The redwood was planted as a symbol of reconciliation over a half-century ago by the family of Nobuo Fujita, a Japanese Navy pilot who dropped incendiary bombs on the forest near Brookings, the Bulletin newspaper of Bend reported.

Firefighters wrapped the redwood in a fire-retardant sheet to protect it, and the flames were believed to be about a mile (1.6 kilometers) away, said Terry Krasko, a spokesman for the firefighters.

Fujita’s two bombs had little effect. He returned to Brookings after the war to apologize.

Saturday was the 75th anniversary of the firebombing. Fujita died in 1997.

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