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Firefighters gained significant ground on the Pilot Fire burning in the Silverwood Lake area Wednesday morning.

A hot and tired fire crew from Folsom marches back to the base after watching for hot spots at the Pilot fire near Silverwood Lake. (Credit: Mark Boster / Los Angeles Times)
A hot and tired fire crew from Folsom marches back to the base after watching for hot spots at the Pilot fire near Silverwood Lake. (Credit: Mark Boster / Los Angeles Times)

Containment of the wildfire increased from just 6 percent Tuesday to 64 percent on Wednesday, according to the federal InciWeb information page on the fire.

The fire had burned 7,861 acres – a little more than 12 square miles — as of Wednesday morning, which was up just 125 acres from Tuesday’s estimate, according to the InciWeb site.

The fire started about 12:10 p.m. Sunday between Pilot Rock Ridge and State Highway 173 in Hesperia.

Investigators have not determined the cause of the fire.

Air quality concerns have prompted the Apple Valley and Hesperia school districts to close all schools again on Wednesday.

Schools in the Silver Valley Unified School District, which were also closed Tuesday, had reopened to students on Wednesday, according to their website.