Hong Kong authorities on Monday arrested 13 people for suspected manslaughter in a probe into the city’s deadliest fire in decades.

Authorities pointed to substandard renovation materials that fueled a blaze that claimed at least 151.

Police continued to sweep the seven towers engulfed in Wednesday’s disaster at the Wang Fuk Court estate, finding bodies of residents in stairwells and on rooftops, trapped as they tried to flee the flames.

More than 40 people are still missing.

A police official, Tsung Shuk, told reporters on Monday, choking up with emotion  that “some of the bodies have turned into ash, therefore we might not be able to locate all missing individuals.’’

Tests on several samples of a green mesh wrapped around bamboo scaffolding on the buildings at the time of the blaze did not match fire retardant standards, officials overseeing the investigations told a news conference.

Contractors working on the renovations used these substandard materials in hard-to-reach areas, effectively hiding them from inspectors, said Chief Secretary Eric Chan.

Foam insulation used by contractors also fanned the flames and fire alarms at the complex were not working properly, officials have said.

Thousands have turned out to pay tribute to the victims, who include at least nine domestic helpers from Indonesia and one from the Philippines, with lines of mourners stretching more than a kilometre (a half-mile) along a canal next to the estate.

Vigils are also due to take place this week in Tokyo, London and Taipei, authorities said.

Amid pockets of public anger over missed fire risk warnings and evidence of unsafe construction practices, Beijing has warned it would crack down on any “anti-China” protests.

At least one person involved in a petition calling for an independent probe among other demands was detained for around two days, sources familiar with the matter said.

Police have declined to comment on specifics, saying only that they will take action in accordance with the law.

The remaining buildings to be scoured for remains are “the difficult ones”, Amy Lam, a senior police official, told reporters on Sunday, adding that the final leg of the search may take weeks.

Images shared by police showed officers clad in hazmat suits, face masks and helmets, inspecting rooms with blackened walls and furniture reduced to ashes, and wading through water used to douse fires that raged for days.

Throngs of officers arrived at the site early on Monday morning to continue their search of the burnt-out buildings.

The apartment blocks were home to more than 4,000 people, according to census data, and those that escaped must now try to get their lives back on track.

Authorities said more than 1,100 people have been moved out of evacuation centres into temporary housing, with a further 680 put up in youth hostels and hotels.

With many residents leaving behind belongings as they fled, authorities have offered emergency funds of HK$10,000 (1,284 dollars) to each household and provided special assistance for issuing new identity cards, passports and marriage certificates.

Residents of Wang Fuk Court were told by authorities in 2024 faced “relatively low fire risks” after complaining about fire hazards posed by the renovations, the city’s Labour Department said.

A department spokesperson said the residents raised concerns in Sept. 2024, including about the potential flammability of the mesh contractors used to cover the scaffolding.

Hong Kong’s deadliest fire since 1948, when 176 people died in a warehouse blaze, has stunned the city, where legislative elections are due to be held this weekend.

On Saturday, police detained Miles Kwan, 24, part of a group that launched a petition demanding an independent probe into possible corruption and a review of construction oversight, two people familiar with the matter said.

Reuters could not establish whether he had been arrested.

Kwan left a police station in a taxi on Monday afternoon, according to a Reuters witness.

Two others have also since been arrested on suspicion of seditious intent, the South China Morning Post said. The police declined to comment on those reported arrests.

China’s national security office warned individuals on Saturday against using the disaster to “plunge Hong Kong back into the chaos’’ of 2019, when massive pro-democracy protests challenged Beijing and triggered a political crisis.

“We sternly warn the anti-China disruptors who attempt to ‘disrupt Hong Kong through disaster’’ the office said in a statement.

“No matter what methods you use, you will certainly be held accountable and strictly punished.’’

(Reuters/NAN)