Fire crews have been at the Yuma Liquidation Store on Foothills Boulevard near 38th Street for at least two hours.
According to a Rural Metro's Facebook post, the fire happened before 2 p.m., and upon arrival, crews found a storage area west of the store "fully involved with multiple structures" impacted.
Border Patrol agents had been investigating cartel scouting activities linked to illegal immigration in the Sierra Pinta Mountains.