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Shares in Macau casino operators have slumped after police arrested 11 people over alleged money-laundering and illegal cross-border gambling.

It comes as authorities had earlier said they were questioning Alvin Chau, a prominent gambling industry figure.

A Chinese state media outlet said Mr Chau was accused of heading a cross-border gambling syndicate.

Casino gambling is illegal in mainland China but legal in Macau, the world’s biggest gambling hub.

It is not clear if Mr Chau was among those arrested, but separately, Hong Kong newspaper the South China Morning Post quoted police as identifying a Macau businessman with the surname Chau.

Mr Chau is the chairman of Suncity Group Holdings. He is also the founder of Suncity – Macau’s biggest “junket operator”, which organises trips to Asian casinos for wealthy gamblers.

Shares in Suncity Group were suspended from trading on the Hong Kong Stock Exchange on Monday. It did not immediately respond to a request for comment from the BBC.

Some of the cities biggest operators were also affected, with MGM China down 10%, Wynn Macau losing 8% and Sands China more than 6% lower.

The Global Times named Mr Chau as the head of a cross-border gambling criminal syndicate, with more than 12,000 gaming agents and 80,000 members across China.

Mr Chau is also a controlling shareholder of Hong Kong-listed Sun Entertainment Group, a film production and cremation services firm, which said in a stock exchange filing on Sunday that its board had noted news coverage about the investigations in Wenzhou and Macau.

“The Board is of the view that the incident does not have any material impact on the financial position, business nor operation of the Group,” the statement said.

Sun Entertainment Group’s shares were down by almost 30% on Monday afternoon.

Macau’s casinos have come under increasing scrutiny in recent months as regulators aim to more closely supervise their operations.

In September, the city’s secretary for economy and finance, Lei Wai Nong, gave notice of a 45-day consultation period on the gambling operators, pointing to shortcomings in supervision of the industry.

During a news briefing, Mr Lei detailed nine areas for the consultation, including better regulation of the industry, as well as having government officials to supervise day-to-day casino operations.

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