The Fire Services Department has launched a probe after a 78-year-old man was found dead in a Lai King Estate fire on Monday.

The blaze broke out at around 5am in a third-floor flat in Wo King House, with the fire area measuring six by five metres.

Assistant divisional officer Wong Cheuk-kei said firefighters found the dead man in bed.

"We rescued three people on the same floor, and another 50 escaped by themselves.

"The fire was put out at about 5.25am."

The three who were rescued suffered from smoke inhalation.

Two of them were sent to Princess Margaret Hospital while the third refused to be hospitalised after being treated at the scene.

Wong said firefighters were still hosing down the flat at around 8am to prevent the blaze from reigniting, as temperatures were still relatively high.

A man, Tse, who lives on the floor where the fire broke out, said: "Once I left my flat, wow, there was a lot of black smoke in the corridor.

"I was a bit scared but I managed to come down here."

Tse said he didn't even have time to put on all his clothes.

Another resident, Yeung, who lives a few floors higher, told RTHK that she noticed a burning smell before the fire alarm started ringing.

A breathing apparatus team and two jets were dispatched to put out the fire.

Police, meanwhile, are looking into the man's cause of death.