Hong Kong’s anti-graft agency arrested 21 people on suspicion of corruption in relation to renovation work at two residential estates, it said on Friday.

Hong Kong has stepped up a crackdown on corruption linked to building renovation following a fire in late November that ripped through seven high-rise towers and killed more than 160 people.

John Lee, the city’s leader, last month set up an independent committee to investigate the fire and the construction industry, and determine whether there was any bid-rigging in the award of contracts.

The Independent Commission Against Corruption (ICAC) said in a statement it conducted enforcement operations last week against a triad-linked corruption syndicate associated with building renovation.

The 21 arrested included middlemen, project consultants, project contractors and members of the owners’ corporation of the two housing estates, the agency added.

In one of the estates, the contractor involved was suspected of bribing the project consultant and some members of the owners’ corporation to obtain a project contract worth HK$33 million ($4.24 million).

In the other estate, the middlemen allegedly collected instruments of proxy, or authorisation tickets from homeowners “by corrupt means” in an attempt to manipulate votes and win future renovation contracts. It did not elaborate.

“Building maintenance is closely related to the public and involves multiple stakeholders. The ICAC has always attached great importance to corruption in building maintenance,” the statement said.

The two estates targeted in last week’s operation were in the Kwun Tong district in eastern Kowloon and not related to Wang Fuk Court, the site of the fire that broke out on November 26.

The ICAC has arrested at least 11 people in a corruption probe into renovation work at Wang Fuk Court.

Residents reacted with anger to the inferno, which took nearly two days to extinguish. Authorities have said substandard building materials used in renovating the high-rise blocks fuelled the fire.