AP) — Authorities warned of poor air quality in central and northern parts of California on Monday due to wildfires in rural areas.

In the northeastern region of the state, mandatory evacuations are in effect for the Hog Fire west of Susanville, which has grown to 9 square miles (23 square kilometers) in Lassen County. Cal Fire says about 170 structures are threatened.

The National Weather Service issued a dense smoke advisory for Lassen and parts of Plumas and Sierra counties due to visibility as low as a quarter-mile (0.4 kilometer).

An air quality alert was also issued for most of the San Joaquin Valley due to smoke from the Mineral Fire in Fresno County west of Coalinga.

The fire has grown to more than 44 square miles (114 square kilometers) and was about half contained. Seven structures have been destroyed and 60 remain threatened.

Several smaller fires burned elsewhere in California, including a 450-acre (182-hectare) blaze in Siskiyou County that triggered an evacuation of the tiny community of Hawkinsville.