More than 50 people have been detained in Shanghai's widening pension fund corruption scandal, a Beijing-funded Hong Kong newspaper has reported.
Yu Zhifei, the head of Shanghai's F1 racing track, has been quizzed
Several senior Shanghai officials and businessmen have already been implicated in the alleged misuse of the multi-million dollar fund.
One of the country's richest men, Zhang Rongkun, was arrested at the weekend.
On Sunday, President Hu Jintao said the Communist Party was determined to root out corruption.
"We are stepping up efforts to improve the rule of law and a culture for clean and honest government, and strengthen the checks and supervision on power," he said.
He also appealed for party unity at a rare joint public appearance with his predecessor Jiang Zemin.
The first high-profile head to roll in the pensions scandal was Chen Liangyu, an ally of Mr Jiang who was dismissed from his post as chief of the Communist Party in Shanghai last month.
Other leading figures tainted by the case include the head of Formula One in China, Yu Zhifei, who has been questioned by the authorities, and the country's chief statistician Qiu Xiaohua who was dismissed from his post.
Zhang Rongkun, believed to be the 16th richest man in China with a $600m fortune, was arrested by "relevant law enforcement authorities", his own firm Fuxi Investment said in a brief statement on Saturday.
SHANGHAI PENSIONS SCANDAL
Labour and social security chief, Zhu Junyi, sacked
District governor, Qin Yu, sacked
City's top Communist Party official, Chen Liangyu sacked
Municipal committee's vice-secretary general, Sun Luyi, sacked
Head of city's F1 motor racing circuit, Yu Zhifei, questioned
Head of China's National Bureau of Statistics, Qiu Xiaohua, (pictured) sacked
One of China's richest men, Zhang Rongkun, arrested
Hong Kong's Ta Kung Pao newspaper reported on Monday that more than 50 other businessmen and government officials were being held over the scandal. It did not give any further details.
As the anti-corruption investigation continues, it seems likely the number of people involved will grow still further, the BBC's Quentin Sommerville in Shanghai says.
More than 100 central government investigators have been sent to Shanghai to investigate money that has disappeared from the city's 10 billion yuan ($1.25 billion) social security fund. The funds were allegedly used to make illegal loans and investments in real estate and other infrastructure deals.
The corruption scandal demonstrates the problems facing those who wish to end graft in China, our correspondent says.
The courts do not operate independently and almost all of those detained in Shanghai have not been seen or heard of since, he adds.
There is little independent oversight. Auditors and corruption investigators are limited and the usual checks and balances that expose corruption - such as a free press and regular open elections - do not exist.