The investigation of bitcoin exchanges, including BTCC, Huobi and OKCoin, was to look into possible market manipulation, money laundering, unauthorized financing and other issues, according to the statements posted on the People's Bank of China's website.

Bitcoin fell from around $909 on the Europe-based Bitstamp exchange to the day's low of $861, leaving it down almost 5 percent .

(Reporting by Jemima Kelly; Editing by Patrick Graham)