Fire crews are trying to contain a forest fire southwest of Wickenburg covering about 420 acres.

Tiffany Davilla, with the Arizona Department of Forestry and Fire Management, said investigators are trying to determine what sparked the blaze.

“We don’t know what the cause of the fire is yet," Davilla said, "but we do know we’ve had three fires in that area in just as many weeks so we’re looking into all of the fires and trying to determine what’s going on in that area."

The fire was 30 percent contained as of early Monday. Davilla said crews hope to have the entire blaze contained in the next few days.