The blaze last week engulfed Wang Fuk Court in the city's northern Tai Po district, becoming the world's deadliest residential building fire since 1980.

Police said the number of dead may still be revised as officers had found "suspected human bones" that require forensic testing.

Mourners continued to stream to a small park near the charred buildings on Wednesday, placing hundreds of bouquets and notes of remembrance for the victims -- the youngest of whom was a one-year-old baby, and the oldest 97.

"I hope people can come here to lay their grief to rest," said visitor Sarah Lam, adding that the victims suffered "many injustices".

"I hope the truth is uncovered swiftly... so they don't need to depart this world bearing such undeserved grievances," she said.

Sections of the park were decorated with lines of colourful origami cranes, and volunteers handed out paper and pens.

Forrest Li, 26, described the location as a "bridge", allowing "communication and the expression of grief through this unspoken connection" with the deceased.

- Netting ditched -

Residents of the sole unaffected tower were allowed to return home briefly on Wednesday to retrieve belongings.

Authorities earlier said the blaze on the estate, which was undergoing major renovations, was likely made worse by the use of netting that did not meet fire-resistance standards.

Flames quickly covered the surfaces of the apartment blocks, which were wrapped with bamboo scaffolding, protective netting and foam boards.

Secretary for Development Bernadette Linn on Wednesday ordered all Hong Kong buildings undergoing major maintenance to remove their netting by Saturday.

Police earlier arrested a total of 15 people, including construction company bosses, on suspicion of manslaughter.

A further six have been arrested on a different charge, over the estate's fire alarms which malfunctioned at the time of the blaze, police said.

- 'No place to hide' -

As well as the outpouring of grief, the disaster has led to calls for accountability and reform.

City leader John Lee has warned against crimes that "exploit the tragedy".

Beijing's national security arm in Hong Kong on Wednesday condemned "external hostile forces (that) have seized upon the disaster to stir up trouble and incite chaos".

"All acts and words aimed at destabilising Hong Kong will be recorded and pursued for life," the Office for Safeguarding National Security wrote in a statement.

"All conspiracies to disrupt Hong Kong will have no place to hide and will be thoroughly extinguished."

Local media reported over the weekend that three people, including 24-year-old student Miles Kwan and former district councillor Kenneth Cheung, had been arrested for sedition.

Both men were later seen leaving police stations.

A student union-run notice board at Hong Kong Baptist University -- nicknamed a "democracy wall" -- was blocked off on Wednesday, an AFP reporter saw.

The message stuck to the board, which remained visible behind tall barricades, read: "We are Hongkongers. Urge the government to respond to public demands so justice can be done."

AFP has contacted the university for comment.