Strong winds of up to 50 mph on Sunday are expected to fan the flames of eastern Arizona’s Wallow Fire, the largest wildfire in the state’s history.

The three-week old Wallow Fire, which has burned over 500,000 acres, is now 38 percent contained. But the hard work of some 4,000 firefighters is threatened by winds that could toss flames miles away and ground special water-pouring helicopters instrumental in the fight against the blaze.

While most of the national attention is on the Wallow Fire, which has moved into New Mexico, down south near the Mexico border the Monument Fire has forced the evacuation of nearly 7,000 people from the town of Sierra Vista by Saturday afternoon.

The Monument Fire, about 20,000-acres large, has also destroyed 47 homes, around the same number as destroyed by the much larger Wallow Fire.

Jonetta Trued, a spokeswoman for the Northern Rockies Incident Management Team, told Reuters that the Monument Fire is about 27 percent contained as of Saturday evening.

Arizona Gov. Jan Brewer on Saturday declared a state of emergency as the Wallow fire crossed state lines. Her declaration allows for the mobilization of the state’s national guard and for the release of $100,000 for emergency response.

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The Wallow Fire began on May 29 by a suspected unattended campfire. Authorities are still investigating how the massive wildfire started, with Forest Service officials interviewing two “persons of interests” this week.