United States Navy minesweepers commenced operations in Brunei Bay on 7 June, and a flotilla of four cruisers and seven destroyers (including an Australian light cruiser and destroyer) served as a covering force. The minesweeping operation was successful, though struck a mine on 8 June and sank with the loss of four lives. Underwater demolition teams investigated all of the landing beaches on 9 June searching for obstacles which could impede the landing craft. The teams assigned to clear obstacles off Labuan were endangered by an unauthorised attack on the island conducted by a force of American B-24 Liberator heavy bombers. Following the landings on 10 June, American Thirteenth Air Force aircraft flying from a base on Palawan Island in the Philippines provided close air support for the forces on Labuan until RAAF units based on the island were ready to take over.