Two helicopter pilots were killed Friday while battling a wildfire in Utah, officials confirmed Saturday.

The pilots died after their Sikorsky Skycrane helicopter crashed Friday morning, according to the Sevier County Sheriff’s Office.

The aircraft was assisting firefighters battling a blaze in the Fishlake National Forest when it went down. The crash sparked a separate fire that later merged with the existing wildfire.

The combined blaze has burned nearly 174 square miles, or about 451 square kilometers, as firefighters continue working to contain the flames.