COLOMBO, Sri Lanka (AP) — A Sri Lankan air force plane crashed on a tea estate in the island’s mountains Friday, killing the four crewmembers on board and injuring a civilian on the ground.

The crash occurred in Haputale district about 200 kilometers (124 miles) east of the capital Colombo, said air force spokesman Capt. Gihan Seneviratne.

Two pilots and two other crewmembers were on the Chinese-built Y-12 aircraft, which was on an observation mission, Seneviratne said.

The Derana television channel reported a woman at the scene where the aircraft crashed sustained injuries and was receiving treatment at a hospital.

It wasn’t immediately clear what caused the crash.

Seneviratne said investigators had been sent to inspect the crash site.