MANILA, Philippines — One U.S. service member and three defense contractors were killed Thursday when a plane contracted by the U.S. military crashed in a rice field in the southern Philippines, U.S. Indo-Pacific Command said.

The aircraft was conducting a routine mission “providing intelligence, surveillance, and reconnaissance support at the request of our Philippine allies,” the command said in a statement. It said the cause of the crash was under investigation.

The Civil Aviation Authority of the Philippines also confirmed the crash of a light plane in Maguindanao del Sur province. It did not immediately provide other details.

The bodies of the four people were retrieved from the wreckage in Ampatuan town, said Ameer Jehad Tim Ambolodto, a safety officer of Maguindanao del Sur. Indo-Pacific Command said the names of the crew were being withheld pending family notifications.

Windy Beaty, a provincial disaster-mitigation officer, told The Associated Press that she received reports that residents saw smoke coming from the plane and heard an explosion before the aircraft plummeted to the ground less than a kilometer (about half a mile) from a cluster of farmhouses.

Nobody was reported injured on or near the crash site, which was cordoned off by troops, Beaty said.

A water buffalo on the ground was killed as a result of the plane crash, local officials said.

U.S. forces have been deployed in a Philippine military camp in the country’s south for decades to help provide advise and training to Filipino forces battling Muslim militants. The region is the homeland of minority Muslims in the largely Roman Catholic nation.