U.S. Indo-Pacific Command says 3 defense contractors also involved in fatal crash.

A U.S. military service member and three defense contractors died Thursday in the Philippines after their surveillance flight crashed, officials say. U.S. Indo-Pacific Command said the aircraft contracted by the Department of Defense went down in the southern province of Maguindanao del Sur and “was providing intelligence, surveillance, and reconnaissance support at the request of our Philippine allies.”

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“The incident occurred during a routine mission in support of U.S.-Philippine security cooperation activities,” U.S. Indo-Pacific Command said in a statement.

“We can confirm no survivors of the crash. There were four personnel on board, including one U.S. military service member and three defense contractors,” it added.

The cause of the crash remains under investigation. The names of those involved are being withheld pending next of kin notification. 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 about half a mile from a cluster of farmhouses.