Between 20.20 and 20.25 hours on 15 Jul, 1942, U-576 fired four torpedoes at the convoy KS-520, the first damaged the Chilore, the second damaged the J.A. Mowinckel, the third sank the Bluefields and the fourth missed the second ship. The U-boat was lost after this attack.

The J.A. Mowinckel (Master Harold Griffiths) was struck by one torpedo in the stern and a second passed astern. The torpedo hit about eight feet below the waterline, blowing a hole in the hull through the after peak and steering engine room. The steering gear, the galley, messrooms and after gun platform were wrecked. The engine room took water because the after bulkhead was ruptured. 11 crew members and 5 armed guards were wounded by the torpedo explosion. One crewman later died of wounds and one armed guard died on 21 July in the Marine Hospital in Norfolk.
The Convoy Commodore on the J.A. Mowinckel joined the Chilore together with USS Spry (PG 64) and decided to head for shoal water to anchor. The Commodore was unaware of a US mine field that extended in an arc of ten miles out to sea from Cape Hatteras to two miles out below Ocracoke Inlet. As the ships headed for the mine field, a US Navy blimb dropped smoke bombs to warn the ships, but they thought it was a warning from U-boats in the area. Four hours after the attack, the Chilore struck two mines and was lost. The J.A. Mowinckel also struck a mine on the starboard side at #2 tank. The anchor was dropped and the 46 crew members and 13 armed guards abandoned ship in four lifeboats after one hour. At 07.30 hours on 16 July, two of the boats landed at Ocracoke Inlet and the other two were towed by a US coast guard boat to the same place.
At 07.00 hours on 20 July, the American tug J.P. Martin towed the tanker to Hatteras Inlet where she was beached and pumped out. On the next day, the vessel was floated, but at 07.00 hours on 22 July, the J.A. Mowinckel struck another mine at #7 tank, which filled with water. The next day, after pumping out this tank, the tugs Relief and USS Scotia towed the tanker to Baltimore for repairs under the escort of two corvettes. They arrived at Hampton Roads on 25 July and then Baltimore for temporary repairs. On 6 September, the vessel left Baltimore in tow for New York, arriving four days later. On 12 Mar, 1943, the repairs were completed and the ship left for Aruba the next day.