Australian gaming tycoon James Packer said Tuesday he was "deeply concerned" about 18 of his Crown Resorts staff detained in China as his board held an emergency meeting to determine what to do next.

The marketing staff were seized in raids late last week, including an executive in charge of luring high-rollers to Australia, with Beijing saying they had been "criminally detained ... for suspected gambling offences".

Shares in Crown plunged more than 13 percent on Monday but stabilised Tuesday, rebounding 1.70 percent to close at Aus$11.34.

"As the major shareholder of Crown Resorts, I am deeply concerned for the welfare of those Crown employees detained in China," said billionaire Packer, who is engaged to pop diva Mariah Carey and is the company's largest shareholder.

"Crown will do whatever it can to support our employees and their families at this difficult time. Our number one priority is to be able to make contact and to ensure they are all safe."

The Crown board held an emergency meeting via phone late Monday amid reports that Chinese police were preparing to charge the employees with organising gambling activities for Chinese nationals overseas.

Gaming companies are not allowed to explicitly advertise gambling in China.

The Sydney Morning Herald said speculation among industry insiders linked the crisis to an attempt by Crown to collect Aus$15 million (US$11.4 million) in gambling debts from a Chinese high-roller at its Melbourne casino.

"I have sought regular updates on this issue and have asked Crown to do everything possible to contact our employees and to support their families, as we await further details from Chinese authorities," added Packer.

"I am respectful that these detentions have occurred in another country and are therefore subject to their sovereign rules and investigative processes."

Crown operates casinos across Australia and the world, including in Macau, where revenues have been hit hard by a Chinese corruption crackdown that has driven away many big-spenders.

Graft has become endemic in China and President Xi Jinping launched a much-publicised anti-corruption drive after he came to power in 2012.

One of those being held is the company's executive vice president VIP International, Jason O'Connor, along with two other Australians.

Australian Foreign Minister Julie Bishop said the government had been notified of their detention in Shanghai and consular officials were making arrangements to visit them.