Federal immigration officials in Washington state arrived on the scene of the largest wildfire in the state on Wednesday and arrested two firefighters who had been working to contain the blaze. Wildfire veterans say it’s nearly unprecedented for federal agents to conduct immigration enforcement near the front lines of an active wildfire.

The Washington Fire was sparked by lightning on Aug. 13 one mile northwest of Washington Park in the Payson Ranger District. The fire has burned 515 acres and is 97% contained.