FRESNO COUNTY (CBS SF) – An air quality advisory has been extended in the Bay Area, as smoke from the Mineral Fire burning in Central California continued to drift into the region.

According to Cal Fire, the fire burning west of Coalinga in Fresno County has scorched 19,500 acres (30.46 square miles) and is 30 percent contained as of Friday morning. Four structures have been destroyed, with another 60 structures being threatened.

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Evacuation orders remain in effect for the community of Bingham Springs and in areas along Highway 198 west of Coalinga to the Monterey County line. No injuries have been reported.

Firefighters on the scene of the Mineral Fire burning in Fresno County. (CBS)

Firefighters on the scene of the Mineral Fire burning in Fresno County. (CBS)

“The fire continues to burn in areas with difficult access and in fuels with no recorded fire history,” the agency said in its update.

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“Containment efforts will be hampered due to extreme fire behavior and challenging weather conditions,” Cal Fire went on to say, with high temperatures in the area expected to be above 100 this weekend.

Smoke from the Mineral Fire has drifted towards the Bay Area for days, leading to hazy skies over much of the region. The Bay Area Air Quality Management District extended its air quality advisory, which was set to expire on Friday, through Saturday.

Residents who smell wildfire smoke are urged to stay indoors, with doors and windows closed and with air conditioners set to recirculated air, the district recommended. People with respiratory illnesses, the elderly and children are urged to take extra precautions.

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The fire, which has been burning since Monday afternoon, is expected to be contained July 21st, Cal Fire said. The cause is under investigation.