ORO VALLEY (AP) — Firefighters were battling two separate wildfires Tuesday in a mountainous area outside of Tucson.

Authorities in the town of Oro Valley said crews made slight progress on a nearby fire in the Pusch Ridge area. The blaze grew to nearly 4 square miles (10 square kilometers) Tuesday evening, according to the U.S. Forest Service. It was 10% contained.

Lightning sparked the wildfire Friday. It is burning in mostly rugged terrain and not threatening any structures.

About 175 firefighters were up against gusty and erratic winds as they worked to build containment lines. They were aided by helicopters that were dousing hot spots with water.

Authorities said increasingly hot and dry conditions this week could hamper firefighting efforts on several wildfires burning around Arizona ahead of the monsoon season.

A second lightning-caused fire was burning through dry grass and brush in rugged terrain north of Oro Valley in the Tortolita Mountains, creating a challenge for the 90 firefighters. It was 25% contained Tuesday evening, according to the Arizona Department of Forestry and Fire Management.

Oro Valley is roughly 15 miles (24 kilometers) north of Tucson.

The Pima County Department of Environmental Quality issued an air pollution health watch Tuesday because of smoke from the two wildfires. The department said the smoke can irritate eyes, the respiratory system and worsen chronic heart and lung diseases.

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