The Allies became aware of the Wizernes site in August 1943 when the Germans began laying extensive new rail sidings which were spotted by RAF reconnaissance flights. Late 1943, a Belgian, Jacques de Duve, supported by German opponents, informed MI5 about the existence of a rocket production site in Saint-Omer. MI5 did not believe de Duve, who was interned for the rest of the war in Latchmere House. In November 1943, the Allied Central Interpretation Unit reported that the Germans had begun constructing the concrete dome and were undertaking tunnelling works in the east face of the quarry. However, it was not until the following March that the Allies added the site to the list of targets for the bombing campaign against V-weapon sites that had already wrecked the Watten bunker and numerous V-1 flying bomb launching sites. Over the next few months, the USAAF and RAF carried out 16 air raids involving 811 bombers that dropped some 4,260 tons of bombs. The bombing caused destruction across a wide area, killing 55 residents of the nearby village of Helfault.