Manila, Feb. 7 -- The Civil Aviation Authority of the Philippines (CAAP) said Friday it is investigating the plane crash that killed one US service member and three defense contractors in Maguindanao del Sur.

The US military-contracted aircraft crashed in Barangay Malatimon, Ampatuan town on Thursday.

"CAAP is working closely with local authorities to determine the cause of the incident," it said in a news release.

The incident involved a Beechcraft King Air 300 with registration number N349CA.

It departed from Cebu and was en route to Cotabato City when it crashed.

"The flight was part of a routine mission in support of U.S.-Philippine security cooperation activities," CAAP said.

"Further details will be provided once the report be...