City leader John Lee, along with senior ministers and dozens of top civil servants, stood in silence for three minutes at 8:00 am (0000 GMT) outside the government headquarters, where the flags of China and Hong Kong were flown at half-mast.

Hours before that, AFP saw citizens placing flowers near the charred shell of Wang Fuk Court, the residential complex that burned for more than 40 hours.

"May your spirits in heaven always keep the joy alive," read a note of remembrance placed at the site.

Condolence points have been set up across Hong Kong for the public to sign condolence books, the government said.

Families have been combing hospitals and victim identification stations hoping to find their loved ones, with around 200 people still listed as missing and 89 bodies unidentified.

On Friday, the city's anti-corruption watchdog arrested eight people in connection with the blaze, the world's worst residential building fire since 1980.

Flames had spread quickly through the housing estate in the city's northern Tai Po district on Wednesday afternoon, engulfing seven of the eight high-rises in the densely packed complex.

Authorities said the cause was yet to be determined, but preliminary investigations suggested the fire started on protective netting on the lower floors of one of the towers and that "highly flammable" foam boards, as well as bamboo scaffolding, had contributed to its spread.

Fire services chief Andy Yeung said they discovered that alarm systems in all eight apartment blocks "were malfunctioning", and vowed action against the contractors.

Residents had told AFP they did not hear any fire alarms and went door-to-door to alert neighbours to the danger.

A man surnamed Fung said he was visiting the housing estate daily to look for his 80-year-old mother-in-law.

"She is on antibiotics... so she is always sleeping. There was no fire alarm, so she might not have known there was a fire," he said.

The city's anti-corruption watchdog said the eight people it arrested on Friday included "consultants, scaffolding subcontractors and (a) middleman of the project".

On Thursday, police said they arrested three men on suspicion of negligently leaving foam packaging at the fire site.

- 'Burning red' -

On Friday, dozens were still in hospital, with 11 in critical condition, and 21 listed as "serious".

AFP journalists saw workers removing black body bags from the site, while vehicles unloaded corpses at a mortuary in nearby Sha Tin.

"We do not rule out the possibility that police will find more charred remains when entering (the building) for detailed investigation and evidence collection," security chief Chris Tang said.

At one hospital, a woman surnamed Wong was looking for her sister-in-law and her sister-in-law's twin, with no luck.

"We still cannot find them. So we are going to different hospitals to ask if they have good news," the 38-year-old told AFP in tears.

The government said police have activated a specialist disaster victim identification system to help locate the missing.

"One building went up in flames and it spread to two more blocks in less than 15 minutes," a 77-year-old eyewitness surnamed Mui told AFP.

"It was burning red, I shudder to think about it."

- Community response -

The blaze was Hong Kong's deadliest since 1948, when an explosion followed by a fire killed at least 135 people.

Lethal fires were once a regular scourge in densely populated Hong Kong, especially in poorer neighbourhoods, but improved safety measures have made them far less common.

Security chief Tang said the full investigation into the fire's causes could take up to four weeks.

Authorities had found temporary accommodation for around 800 people, the government said Friday.

Nine emergency shelters were also in operation, accommodating around 720 people overnight.

A spontaneous community effort to help firefighters and those displaced has become a well-oiled machine.

Separate supply stations for clothes, food and household goods were set up at a public square near the towers, as well as booths providing medical and psychological care.

So much was donated that organisers put out a call on social media saying no more was needed.