The force on Saturday said two people were arrested on Thursday night after officers searched a premises in Mong Kok and seized four fake ID cards, 36 partly completed fake ID cards and two “green cards”, needed to seek employment in the city.

Construction workers must complete a safety course and get a “green card” before they are eligible to work on building sites.

“We do not rule out the possibility that the two arrestees were creating fake identification documents for illegal immigrants to look for jobs in Hong Kong,” Chief Inspector Yan Fong-wai of the Organised Crime and Triad Bureau said.

He added that the workshop is alleged to have made forged ID cards in two grades, priced at HK$1,600 for the higher quality ones and HK$1,200 for the others.

The two people arrested were aged 30 and 64 and of Vietnamese origin.

They were said to be holders of recognisance forms, which allow them to live in Hong Kong, but not to work.

The pair are expected to appear at West Kowloon Court on Monday charged in connection with the alleged offences.

Another 423 people, aged between 16 and 80, were arrested across the city between Thursday and Saturday for alleged offences including money laundering, conspiracy to defraud and possession of prohibited weapons.

Police detained 248 men and 175 women, 373 of them Chinese.

The force said it shut down three illegal gambling premises operated by triads.

Kowloon West regional crime unit also arrested 86 people in separate operations launched between July and August after intelligence showed a dispute between two criminal syndicates.

Four of the people arrested, aged between 33 and 51, were said to be leaders of two non-Chinese criminal syndicates suspected of conspiracy to traffic in dangerous drugs.

The rest, aged between 16 and 66, were suspected of offences including managing a brothel, drug trafficking, the sale of illicit cigarettes and possession of counterfeit goods.

The force said some those detained were found to have triad backgrounds.

Officers inspected 25 premises alleged to have been used for criminal purposes, including gambling and storage of goods worth HK$1.2 million, which were seized.

Police confiscated drugs including marijuana, methamphetamine and cocaine.

Black market cigarettes and alcohol, as well as counterfeit designer handbags and watches were also seized.

“We have cracked two non-Chinese criminal syndicates,” Chief Inspector Tai Po-yee of the Kowloon West regional crime unit said.

“We have successfully cracked down on their main source of income.”