Macau police have arrested over 100 people - including gaming tycoon Stanley Ho Hung-sun's nephew Alan Ho and 96 alleged prostitutes - in a crackdown against vice operations at a hotel.

A syndicate has allegedly controlled 100 rooms in the hotel since 2013. Ho, 68, and five hotel staff were among those detained.

Police said the six allegedly conspired to run the prostitution syndicate with a profit of 400 million patacas for a year at the hotel, which was not named, in the area between the main ferry terminal and the Hotel Lisboa. It is the largest sum involved in such a case since the gaming enclave was returned to China in 1999.

Alan Ho is a senior executive of the Hotel Lisboa and has also been chairman of the Association of Macau Tourist Agents and vice-chairman of the Macau Hoteliers and Innkeepers Association.

A police spokeswoman said the six were yesterday transferred to the public prosecution office, which will decide whether to lay charges against them.

They were arrested at the hotel during an operation on Saturday, in which over one million patacas in cash, suspected to be the proceeds of crime, was seized.

It is alleged the ring sourced prostitutes online, mostly from the mainland, then arranged for them to come to Macau.

Police said the women had to pay the ring a "membership" fee of 150,000 yuan (HK$190,000) a year, plus a monthly "protection" fee of 10,000 patacas before they could use the hotel rooms.

The protection fee allowed the women to hunt for clients in the hotel's lobby. They could keep the money they earned, which ranged from the equivalent of HK$1,500 to HK$5,000 per day.

The five hotel employees arrested were a senior manager, a manager, a security manager, a lobby receptionist and a driver. They were aged from 32 to 57. The security manager was a Hong Kong man, the manager and driver were from Macau and the senior manager and receptionist were mainland women.

Another 95 mainland women and one Vietnamese woman who were alleged prostitutes were also arrested. Of them, 20 were illegal immigrants and 10 used forged identity documents, police said.

A list of 2,400 women, believed to have joined the syndicate as prostitutes, was found on a computer.

Police made the arrests after receiving a tip-off last April.

He received a medal from the Macau government in 2012 in recognition of his contribution to the tourism industry.

According to a December 2008 press release published on SJM Holdings' website, Alan Ho was on the management committee of the Macau casino operator, controlled by the family of Stanley Ho.

SJM could not be reached for comment on Alan Ho's current position.