US authorities suspected that a British man accused this week of causing the 2010 'flash crash' was making illicit trades back in 2009 it's been revealed, with experts expressing shock that it took six years for charges to be brought. Navinder Singh Sarao, 36, is accused of making £26million from illegal trades over five years and an investigation team involving six agencies in the US and Britain want him put on trial in New York. But analysts are bewildered that it's taken this long for action to be taken. US authorities suspected that British man Navinder Singh Sarao (circled) accused this week of causing the 2010 'flash crash' was making illicit trades back in 2009 . US prosecutors believe Mr Sarao used special computer software to manipulate the market on Wall Street . 'Flash crash': Sarao is accused of causing the Wall Street 'Flash Crash' on May 6, 2010, when £570billion ($850 billion) was wiped from the value of America's biggest companies in five minutes . Sarao was warned about his trading in 2009 by officials at the self-regulatory Chicago Mercantile Exchange (CME), where he was making transactions. However, he continued his alleged manipulation well into this year. Dave Lauer, president of lobbying and research firm Kor Group, told Bloomberg that he was gobsmacked at the pace of the investigation. He said: 'How this continued for six years when the CME appeared to know about it, it kind of boggles my mind. This is about as simple and easy as you can get, and it took them this long to do anything about it.' Edgar Perez, author of Knightmare on Wall Street and The Speed Traders, meanwhile, asked: 'Why would regulators let Sarao operate in the markets and engage in similar trading strategies as in the Flash Crash eight more times?' Sarao allegedly triggered – from his home computer in Hounslow, London – the Wall Street 'Flash Crash' of May 2010, in which almost a trillion dollars was wiped from global share prices, using a series of fake transactions. Trader Navinder Singh Sarao, 36, is shown here at Westminster Magistrates' Court after being arrested over illicit trading . A flash crash is a sudden plunge in stock prices. On May 6, 2010, the US stock market dramatically collapsed – wiping billions off the world's biggest companies. Between 2.42pm and 2.47pm, the Dow Jones shed 600 points, having already been down more than 300 points – a startling 6 per cent fall in just five minutes. Very soon it had recorded an almost 1,000-point loss on the day. But, by 3.07pm, the market had miraculously regained most of the 600-point drop – making the flash crash the second-largest point swing ever recorded. Hours later, European markets opened and crashed in similar fashion. The UK's FTSE 100 fell 138 points, France's Cac shed 163 points, and Germany's Dax dropped 193 points. The cause of the crash puzzled US officials. Theories included technical glitches, high frequency trading or changes in market structure – but never criminal activity. He allegedly used automated trading software to 'spoof' the market by placing up to 19,000 orders and then cancelling them, all in under one second. However, manipulation wasn't identified as the cause of the crash in a September 2010 report, suggesting that regulators did not see his activity at that time. Tim Massad, the head of the Commodity Futures Trading Commission, which oversees the trading of futures and swaps, said on Wednesday that it took so long to charge Sarao because of the size and complexity of U.S. derivatives markets. 'These are huge markets,' he said. 'There's a lot going on.' The agency, which oversees self-regulatory bodies such as the CME, brought civil charges against Sarao alongside criminal charges by the Department of Justice. The many years it took for the CFTC to come out with its findings, and the fact that manipulation wasn't mentioned in the 2010 report, suggested that the help of a whistleblower was essential in bringing the charges, one lawyer said. 'This can't have been a five-year continuous investigation, can't have been,' said the lawyer, who is familiar with the CFTC's thinking, and who asked to remain anonymous. 'Something happened some period later where this came up again. 'If there was any indication that there was manipulation behind this, given the profile of this, the agency would have proceeded. It wouldn't have taken five years.' Scotland Yard's extradition unit arrested Sarao on Tuesday night at the request of the FBI, which claims he set up an offshore company in the Caribbean called 'Nav Sarao Milking Markets' and arrogantly told financial officials to 'kiss my a***'. In West London, neighbours of the man now dubbed the 'Hound of Hounslow' were puzzled by his supposed wealth, saying he lived humbly.
Navinder Singh Sarao, 36, is accused of causing the May 2010 'flash crash'
Officials believe that he used software to make fake transactions .
He was first warned about alleged illicit trading back in 2009 .
Sarao continued his alleged manipulation well into this year .
'How this continued for six years  kind of boggles my mind' - Analyst .