Firefighters are still searching for hundreds of missing people after a massive fire tore through multiple high-rise residential buildings in Hong Kong.

At least 65 people died in the blaze - the city's deadliest in more than 70 years - at Wang Fuk Court's complex, which is home to thousands.

The tower blocks had been undergoing extensive renovations - and while the exact cause for the fire is unclear, police say materials on the outside of the buildings may have facilitated its spread.

Three construction company executives have been arrested on suspicion of manslaughter and gross negligence, and Hong Kong's chief executive John Lee has vowed to launch a comprehensive investigation.

The fire, which tore through seven of eight tower blocks in Tai Po district on Wednesday, is now basically under control, Lee said.

It started at 14:51 local time (06:51 GMT) on Wednesday, with flames and thick clouds of grey smoke seen billowing from the towers, dominating the city's skyline.

By 18:22 local time, officials upgraded the fire to a level five - the most serious category.

Firefighter Ho Wai-ho, 37, was among those killed in the blaze. He was found collapsed at the scene about 30 minutes after contact with him was lost.

Ten other firefighters are also injured, the fire department said.

The fierce heat of the blaze, as well as dangerous debris and the risk posed from collapsing scaffolding, has hampered rescue efforts, but the fire department has so far rescued 55 people.

More than 270 people remain unaccounted for, while 70 people are injured.

The mood in Hong Kong has shifted from shock to anguish, as questions grow regarding who should be held accountable for the blaze. Anger has been building on social media, especially after several residents revealed in interviews that they did not hear a fire alarm when the fire broke out.

Reports of their complaints last year over renovation plans have also resurfaced, and are circulating widely online. Residents had taken issue with high renovation fees and questioned whether the materials used complied with fire-safety regulations.

Mesh material and plastic sheets which were found on the outside of the buildings are not believed to be fireproof, while polystyrene was also found on the buildings' windows.

These materials may have allowed the fire to spread faster, police said.

Hong Kong's Independent Commission Against Corruption has said it will launch a criminal investigation over the renovation works.

Lee said he had arranged inspections of all housing estates undergoing major repairs to check the safety of scaffolding and building materials.

He added that the government was considering a review of bamboo scaffolding and whether they should be replaced by metal frameworks.

China's President Xi Jinping has expressed sympathy for the victims and urged that every effort be made to put out the fire and minimize the losses, state media reported.