A former mayor from Guangdong province is being investigated for alleged insider trading, authorities said on Thursday.

Li Qihong, who had been mayor of Zhongshan, is being investigated along with her husband and relatives.

They are suspected of having illegally earned 19.8 million yuan ($3 million) from insider dealing on the stock market during a two-month period in 2007, according to Zhao Zhenhua, deputy secretary of the provincial Party's commission for discipline inspection.

Five of Li's relatives are part of the probe, Zhao said.

At the time, Li's husband, Lin Yong'an, 54, had been vice-chairman of the Zhongshan city association of golf, while her younger brother, Li Qiming, had been the manager of a local property development company.

Investigators believe they may have raised a total of 6.7 million yuan to buy stock in Zhongshan Public Utilities Groups Co Ltd, a Shenzhen-listed company, in August 2007.

During the 14 successive trading days after Li allegedly purchased the stock, the company's price rose dramatically. Investigators believe Li revealed changes to the company in advance and therefore pushed the stock price high, Zhao said.

After her case was made public at the end of May 2010, she was removed from her post.