Four people were sent to hospital and about 100 others evacuated after fire broke out at a public housing block in Tseung Kwan O on Tuesday morning.
One male resident suffered serious burns while three others felt unwell suffering from smoke inhalation. About 100 residents had to be evacuated to an open area on the ground.
The blaze started at the 10th floor unit in Tak Yue House of Hau Tak Estate around 9.30am.
The unit spewed burning flames and dense soot that blacked the walls and windows of the three floors above, local TV footage showed.
Firemen extinguished the fire about 10.30am.
They were investigating the cause of the blaze.