(AP) — Four hundred firefighters are now battling the Arizona wildfire that killed 19 firefighters.

Yavapai Community Health Services says 200 more firefighters have joined the fight. Hundreds of people are evacuated, and shelters are set up for residents.

An automated call warning people to evacuate was sent, and sheriff’s officers are going door-to-door to make sure people get out of their homes.

The lightning-sparked fire — which had exploded to about 13 square miles by Monday morning — destroyed about 50 homes and threatened 250 others in and around Yarnell, a town of 700 people in the mountains about 85 miles northwest of Phoenix.