At a Thursday briefing, Macau’s Judiciary Police announced that earlier in the week, 113 people had been arrested for allegedly being involved in a long-running loan sharking operation that reportedly targeted customers of the former Portuguese colony’s casinos.

GGRAsia reports that according to Macau police, the operation involved the unlawful loaning of an estimated minimum of HKD70 million (US$8.92 million) in total. Officers on Thursday reportedly communicated that the action by the city’s police had seen more single-case arrests in the city since the December 20, 1999 return to Chinese sovereignty.

Tuesday raids at 21 flats “around the Cotai area” prompted the arrests, according to police. Citing a press briefing by police, local Chinese-language news media reported that included among the items seized were watches and jewelry, loan slips, account books, HKD2 million in cash and gambling chips with a reported HKD100,000 face value, GGRAsia reports.

Known as usury under Macau law, the alleged loan sharking enterprise was reportedly viewed as being “highly-organized” and having featured “strong techniques” for dealing with police surveillance, as told to the media by the Judiciary Police. The Macau police are of the mind that the operation might have been in existence since 2011.

It wasn’t until 2016, however, when police first received intelligence regarding the matter, at which point it initiated a series of investigations, said Fong Hou In, the head of the support and intelligence department at the Judiciary Police.

Highly organized, the alleged loan sharking operation reportedly had a strict division of tasks assigned to its members, including the pursuit of accounting functions, identifying gamblers who were potential borrowers and issuing credits. According to the police, those gamblers who failed to repay their debts were confined illegally by the group.

The police believed that of the more than 100 people arrested, one was a Hong Kong resident and the operation’s ringleader, with most of the members of the alleged loan sharking ring residents thought to be mainland China residents.

GGRAsia reports that in Q1 of this year, gaming-related loan sharking cases swelled by 15.9% year-on-year to 102, according to police data. During that time frame, 59 total cases of gaming-related suspected illegal detention were on record, a 43.8% decline compared with the period the year prior.