China's sacked railways minister is under investigation for allegedly embezzling more than 800m yuan (£75m; $121m), state media report.
Liu Zhijun was forced to stand down last month after the authorities launched an investigation for "serious disciplinary violations".
Mr Liu is alleged to have received huge bribes when handing out contracts for the country's high-speed rail network.
He has not publicly commented on the allegations against him.
No official charges have yet been filed against the minister. The Ministry of Railways could not be reached for comment.
Mr Liu had served as the railways minister since 2003, leading an ongoing multi-billion dollar investment programme in China's railway network.
He is currently the most senior official to be investigated by the authorities.
Ministers are rarely targeted in corruption crackdowns as it could damage the credibility of the Communist Party, says the BBC's Martin Patience in Beijing.
But the country's leadership has promised to take a tougher line knowing that corruption is a major source of public anger, our correspondent says.
Earlier this year, President Hu Jintao warned that the situation was "grave" and that it would require long-term efforts.
Last year, China publicly admitted in a report that its corruption problem was "still very serious", setting out new measures to tackle it.
The report said that more than 200,000 cases - including embezzlement and bribery - had been investigated since 2003.
The document was released after the introduction of new rules requiring members of the governing Communist Party to report incomes and investments.
However, critics say corruption is ingrained in the system and new regulations will not solve the problem.