An Australian-Chinese woman whose family has a lucrative real estate business in Tianjin has asked legal authorities to investi gate her claim that a Bank of China branch illegally released her PIN number and allowed 55 million yuan (HK$51 million) to disappear. The Australian citizen said she was prepared to sue the Heping branch, which she claims is responsible for her loss. The manager of the Heping branch said she did not know what had happened to the account, except that local police had ordered the bank to freeze it in December due to 'some problem'. The manager would not comment further on the case. Chinese-born Ma Ping, showing photocopied deposit slips to journalists, said the amount allegedly withdrawn by unknown parties were three deposits made between October 1999 and January last year in the name of Zhang Mu, her husband, and a business called Tianjin Xinwan Real Estate Development Co Ltd. The family operates shopping malls in Beijing and Tianjin. Speaking in Beijing last week, Ms Ma alleged someone had obtained her personal identification number, adding: 'The situation is causing us a lot of trouble. 'I fought with my husband, and he left me. His family was very worried.' Ms Ma, who said she returned to China as an investor, hired a Beijing lawyer to investigate. The lawyer, Guan Anping, said he interviewed the branch manager about five times and learned that a bank employee had released Ms Ma's identification number, allowing others to access the money and drain the account. The lawyer said the case bore all the hallmarks of corruption. Mr Guan wrote the Tianjin Public Security Department a six-page letter on July 12 asking police to take up the case. He said yesterday the police had not responded to the request. A police investigation into the case would be the first step in preparation for a lawsuit against the people responsible for the alleged scam, the lawyer said. The Bank of China is one of the country's four major commercial banks. It had aggregate assets of 3,168 billion yuan last year. Sources said the bank was planning to become listed in two years' time. No one was available for comment at the Bank of China's head office in Beijing. Ms Ma said she had approached city officials and party officials in Tianjin about her bank account. She said that because she had invested money in Tianjin, the officials had listened to her case and voiced their support for an investigation. Chinese authorities have highlighted economic violations and bank fraud as key targets of their anti-corruption campaign. Computer systems aimed at improving monitoring of the flow of funds are rare in Chinese banks, observers say.