The Fire Services Department said on Wednesday evening it's difficult to predict when a No. 5 alarm blaze in Tai Po – which claimed at least 13 lives and injured 15 others – would be put out.

Speaking in a media briefing some five hours after the blaze started, a deputy fire services director, Derek Chan, said scaffolding at Wang Cheong House at Wang Fuk Court caught fire first, and it quickly spread to all but one of the estate's eight blocks.

Chan described the situation in three of the eight blocks ablaze as severe.

"We received numerous assistance calls from the public, and also debris and scaffolding of the affected buildings are falling down, so they pose additional danger to our frontline personnel," he said.

"Besides, the temperature inside the buildings concerned are very high. It's quite difficult for us to enter the building and go upstairs to conduct firefighting and rescue operations."

Chan said more than 750 firefighters and paramedics have been deployed in the operation.

Police said people who need to find out about the deceased and injured can call a police hotline 1878-999.

Officers have been closing off parts of the nearby area, and the public is advised to avoid the area in general.

The government added that more than 700 people have sought temporary shelter.