Chinese authorities said Tuesday that a former top official of the country's first free trade zone (FTZ) in Shanghai was under investigation for violating the law, following months of uncertainty about his fate.

Shanghai's corruption watchdog said Dai Haibo, previously Communist Party chief and executive deputy director of the FTZ, was under investigation for "severe" violations of discipline and the law, according to a statement.

It gave no details of his alleged crimes, but violation of discipline is a phrase typically used by the ruling party to refer to corruption.

State media announced Dai's removal in September, a year after the FTZ was launched to great fanfare. He was also a deputy secretary of the city government in China's commercial hub at the time.

Dai was the public face of the FTZ, appearing at news conferences, meeting foreign delegations and running the zone's administration on a day-to-day basis.

Chinese President Xi Jinping launched a much-publicised drive against corruption after he came to power two years ago, vowing to target both high-level "tigers" and low-ranking "flies".

There has been speculation over whether Xi might target Shanghai, where he was the city's party chief on his rise to the top post.

Shanghai is believed to enjoy political protection as the power base of former president and Communist Party chief Jiang Zemin.

Reforms in the FTZ have disappointed so far. The government originally promised a range of financial changes, including full convertibility of the yuan currency and free interest rates, which remain unfulfilled.

The American Chamber of Commerce in Shanghai reported earlier this month that 73 percent of the 377 companies responding to its annual business climate survey said the FTZ offers "no tangible benefits" for their business.

China has already announced plans to expand some reforms from the first FTZ nationwide, while three more locations intend to set up their own zones.

A commerce ministry spokesman said Tuesday that plans for the launch of similar zones in Guangdong and Fujian provinces, as well as Tianjin municipality, are awaiting central government approval. Media reports have said the Guangdong FTZ could be launched as early as Wednesday.