Police continue 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 missing.
"Some of the bodies have turned into ash, therefore we might not be able to locate all missing individuals," Tsung Shuk Yin, a police official told reporters on Monday, choking with emotion.
Tests on several samples of a green mesh that was 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, in effect hiding them from inspectors, Chief Secretary Eric Chan said.
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 along a canal next to the estate.
Vigils will also take place this week in Tokyo, London and Taipei.
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 about two days, sources familiar with the matter said.
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 might 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 on Monday morning to continue their search of the burnt-out buildings.
The apartment blocks were home to more than 4000 people.
More than 1100 people have been moved out of evacuation centres into temporary housing, with a further 680 put up in youth hostels and hotels, authorities said.
With many residents leaving behind belongings as they fled, authorities have offered emergency funds of 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 they faced "relatively low fire risks" after complaining about fire hazards posed by the renovations, the city's Labour Department said.
The residents raised concerns in September 2024, including about the potential flammability of the mesh contractors used to cover the scaffolding, a department spokesperson said.
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.
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.
