LONDON , England -LRB- CNN -RRB- -- A neighborhood in east London was getting back to normal Saturday after British Army engineers detonated a large World War II bomb unearthed this week on a building site , officials said . Army engineers covered the bomb with sand to minimise the risk of an explosion . An Army bomb disposal team carried out a controlled explosion on the 2,200-pound German warhead at 5:55 p.m. -LRB- 12:55 p.m. ET -RRB- Friday , London 's Metropolitan Police said . Video of the blast showed brown dirt , debris and black smoke shooting into the air when the bomb went off . There were no reports of any injuries or damage to surrounding property after the blast , the police and Ministry of Defense said . The public was allowed back into the industrial neighborhood by Friday night , authorities said . Two subway lines and a rail line in the area , which were shut down after construction crews discovered the bomb Monday , were running normal service Saturday , transportation officials said . London 's transit authority , Transport for London -LRB- TfL -RRB- , said the police and army gave permission for its engineers to check the tracks less than an hour after the controlled explosion . The tracks were clear of debris and damage and services resumed at 7:13 p.m. -LRB- 2:13 p.m. ET -RRB- , TfL said . Contractors preparing a waterway near the site of the future Olympic Park discovered the bomb Monday . The Ministry of Defense said the bomb , which measured four feet by two feet , was the largest one found in the capital since 1975 . The bomb was `` enormous , '' said Simon Saunders , a spokesman for the British Army 's London district . At one point during the week the bomb started ticking , which suggested a timing device , Saunders said . Disposal experts put strong magnets next to the bomb to shut down the clockwork and the ticking stopped , he said . It 's not uncommon for World War II-era bombs to be unearthed in Europe . In London , which suffered the aerial bombardment of the Blitz , bombs are uncovered two or three times a year , Saunders said . The London Blitz lasted from September 1940 until May 1941 . German bombers attacked the city every day or night for the first two months , but the worst night was the last -- May 10 , 1941 , when 3,000 people were killed in London , according to the Museum of London . Much of the Blitz focused on east London . In all , more than 20,000 people were killed in the Blitz , short for `` Blitzkrieg , '' the German word for `` lightning war . ''