and commercial centres were heavily damaged, the electrical supply was knocked out, and five oil tanks and two magazines exploded. Nine days later, two waves of 125 and 170 bombers dropped heavy bombs, including 160 tons () of high explosive and 32,000 incendiaries. Much of the city centre was destroyed. Damage was inflicted on the port installations, but many bombs fell on the city itself. On 17 April 346 tons () of explosives and 46,000 incendiaries were dropped from 250 bombers led by KG 26. The damage was considerable, and the Germans also used aerial mines. Over 2,000 AAA shells were fired, destroying two Ju 88s. By the end of the air campaign over Britain, only eight percent of the German effort against British ports was made using mines. In the north, substantial efforts were made against Newcastle-upon-Tyne and Sunderland, which were large ports on the English east coast. On 9 April 1941, Luftflotte 2 dropped 150 tons () of high explosives and 50,000 incendiaries from 120 bombers in a five-hour attack. Sewer, rail, docklands, and electric installations were damaged. In Sunderland on 25 April, Luftflotte 2 sent 60 bombers which dropped 80 tons () of high explosive and 9,000 incendiaries. Much damage was done. A further attack on the Clyde, this time at Greenock, took place on 6 and 7 May. However, as with the attacks in the south, the Germans failed to prevent maritime movements or cripple industry in the regions. The last major attack on London was on 10/11 May 1941, on which the Luftwaffe flew 571 sorties and dropped of bombs. This caused more than 2,000 fires; 1,436 people were killed and 1,792 seriously injured, which affected morale badly. Another raid was carried out on 11/12 May 1941. Westminster Abbey and the Law Courts were damaged, while the Chamber of the House of Commons was destroyed. One-third of London's streets were impassable. All but one railway station line was blocked for several weeks. This raid was significant, as 63 German fighters were sent with the bombers, indicating the growing effectiveness of RAF night fighter defences. RAF night fighters German air supremacy at night was also now under threat. British night-fighter operations out over the Channel were proving successful. This was not immediately apparent. The Bristol Blenheim F.1 carried four machine guns which lacked the firepower to easily shoot down a Do 17, Ju 88 or Heinkel