At 15.46 hours on 11 March 1941 the unescorted Memnon (Master John Parry Williams) was hit on starboard side underneath the aft mast between holds #5 and #6 by one G7e torpedo from U-106 while steaming on a zigzag course at 16 knots in clear weather and moderate sea with a heavy swell about 220 miles west of Cape Blanco, French West Africa. The ship had been warned about the presence of a U-boat in the vicinity and passed an empty lifeboat about two hours before the attack, but the Germans managed to submerge and reach such a favorable attack position only 80 minutes after spotting the fast ship that the torpedo could be fired from a distance of less than 400 meters. The explosion blew the hatch covers off, threw some of the ore carried as cargo over the deck and buckled the plates on the starboard side. The 62 crew members, two gunners (the ship was armed with one 4in, one 12pdr and one machine gun) and six passengers (RAAF personnel) began to abandon ship in four lifeboats. However, the two port boats were on the weather side and rendered unseaworthy as they were forced across the after deck by the waves. Their occupants, provisions and gear were later transferred to both intact starboard lifeboats. The ship quickly settled by the stern on an even keel with water reaching the aft gun platform within three minutes, forcing the gunner and two sailors who had remained at the gun to float off the stern on a raft. The two wireless operators were the last men to leave the ship after sending a distress signal and were picked up by the boats after jumping overboard. The Memnon sank by the stern about 15 minutes after being hit on starboard side aft by a second G7e torpedo fired as coup de grâce at 15.47 hours. U-106 surfaced astern of the sinking vessel to question the survivors and while doing so pointed out two Chinese sailors swimming in the water, who were subsequently rescued by the lifeboats. Four crew members were lost.

As the distress signal had been received by a Spanish ship about 200 miles away, the master decided to stay on the sinking position in hope they came to their assistance, but apparently they did not even report it to the British authorities. After 36 hours the two starboard boats set sail and kept together despite a very heavy sea. The smaller boat was in charge of the master and as it was sailing faster it went ahead in order to send help to the other boat when reaching the coast. It arrived off St. Louis after five or six days, but landing was too dangerous due to the surf so they decided to head for Dakar, passing a French steamer en route that did not notice the boat despite burning a flare. Dakar was reached on 21 March and a local fisherman piloted the lifeboat to Yoff from where all 22 survivors were quickly taken to a hospital due to their weakened state. The other lifeboat in charge of the chief officer reached the coast about 30 miles north of St. Louis on 20 March, but on the same day one occupant died of exposure and was buried at sea. They met a local fisherman who tried to guide the boat over the sand bar at the mouth of the river Senegal. However, the sea proved to be too rough so they decided to proceed to Dakar, arriving off the harbor during the morning of 23 March. There they met the French motor merchant Kilissi which had just left that port bound for Casablanca. The chief officer went aboard and the French master provided him with a chart, gave provisions and water to the men in the boat and agreed to land the boatswain and second steward at Dakar as they were both in a much debilitated condition. The lifeboat with 24 European and 13 Chinese crew members, one gunner and three passengers then proceeded to Bathurst and was towed in by the launch of the harbormaster in the evening of 24 March.

All survivors at Dakar were interned by the Vichy French authorities, but after 25 days all seven Chinese survivors were allowed to leave across the border to Bathurst together with the master, chief engineer officer, boatswain and another crew member. Only 14 men of military age, including one gunner and three passengers, were taken to an internment camp at Koulikoro in French Sudan. Three of these men escaped from captivity in April and tried to reach British territory by following the river Niger, but were caught near the border. On 29 May 1941 all internees were taken to Kaolack and allowed to leave to Bathurst in exchange of two gallons of petrol and seven French prisoners for each of the British.