At 05.23 hours on 17 April 1942 the unescorted and unarmed Heinrich von Riedemann (Master Andrew Weiler) was hit by one torpedo from U-66 on the port side in the way of #6 tank. The explosion wrecked the steering gear and the port diesel engine. The ship was pouring oil from the tank while steering circles until the other engine was stopped. 20 minutes after the hit, the ship was abandoned in three lifeboats. At 06.40 hours, another torpedo hit the ship setting her on fire, which went out after 25 minutes. At 07.55 hours, a third torpedo struck and set the ship on fire again. The tanker finally sank at 09.05 hours.
The boat of the master containing 15 men landed at Blanquilla Island at 01.00 hours on 18 April, the survivors were picked up on 20 April by the steam merchant Maricaibo and landed at Caracas two days later. 29 men in two lifeboats were picked up by the Karmt at 13.30 hours on 17 April and landed at Trinidad one day later.