Hong Kong authorities are investigating possible corruption and severe negligence after a massive blaze swept through a residential complex this week, killing at least 128 people in the city’s worst fire disaster in decades.

The fire erupted Wednesday at the Wang Fuk Court estate in the city’s northern New Territories, engulfing seven of its eight residential towers. The complex housed nearly 4,800 people, some of whom had warned officials last year about fire safety risks linked to ongoing renovation work.

Police initially arrested three construction workers on suspicion of manslaughter and gross negligence, later releasing them on bail. Another eight individuals — scaffolding subcontractors, engineering consultants and renovation project managers — were detained as part of a widening corruption probe. Authorities did not name the company involved, though documents from the homeowners’ association list Prestige Construction & Engineering as the main contractor. Boxes of records have been seized from its offices.

Investigators are focusing on the materials used in the renovation, particularly the scaffolding netting and highly flammable foam panels. Early findings suggest the blaze began in the lower-level scaffolding net before spreading rapidly as foam insulation caught fire, said Security Secretary Chris Tang. Fire officials also discovered that several alarms in the estate, which houses many elderly residents, failed to activate.

Firefighters battled the inferno for 40 hours, prioritizing units from which emergency calls had been received. Seventy-nine people were injured, including 12 firefighters, and one firefighter died in the operation. Smoke continued to drift from the charred towers even two days later.

Rescuers have now completed searches, though more bodies may be recovered. Authorities say 89 sets of remains are awaiting identification, while roughly 200 people were initially reported missing.

Among the victims were two Indonesian domestic workers, and 11 more remain unaccounted for, Indonesia’s foreign ministry said.

Flags across the city flew at half-mast on Saturday as Chief Executive John Lee led officials in a three-minute silence to honour the dead. The tragedy marks Hong Kong’s deadliest fire since a 1996 commercial building blaze killed 41 people, and the deadliest overall since a 1948 warehouse fire claimed 176 lives.