OSAN AIR BASE, South Korea — A grass fire broke out Monday in a remote area and spread to Osan Air Base, sending plumes of gray smoke into the sky for nearly three hours.

The area near the base’s golf course was evacuated as helicopters dropped water on the flames and firefighters worked to extinguish them on the ground.

The 51st Fighter Wing said the blaze consisted of three separate spot fires contained shortly before 5 p.m., when the evacuation notice was lifted.

Helicopters used the golf course’s water hazards, just a few hundred yards from the fire, as fill stations for their buckets.

Bulldozers and other heavy equipment were seen heading toward the fire after it was contained.

“All individuals with reactive airway disease and/or asthma are advised to stay indoors or avoid areas with thick smoke until further notice,” the 51st Fighter Wing said at about 5 p.m. on its Facebook page.

The fire began around 2:10 p.m. in a field of reeds, although the cause was still under investigation, said a South Korean fire official in Osan, who spoke on condition of anonymity. He said there were no houses in the area and nobody was hurt.

Stars and Stripes reporter Yoo Kyong Chang contributed to this report.

fichtl.marcus@stripes.com