The Fire Services Department said a man has died and his wife is in critical condition following an early morning fire at a Yuen Long residential estate on Sunday.

Authorities received multiple reports of a blaze in a flat at YOHO Town at approximately 6.19am.

Firefighters arrived on the scene within three minutes and extinguished the fire in about 20 minutes.

Officers said a married couple was found unconscious inside the flat, in which both were given emergency treatment at the scene before being rushed to hospital.

"The female victim is in critical condition and has fallen unconscious. She was treated on-site and then transported to Tuen Mun Hospital for further care," said Ambulance Officer Kung Yui-lung.

"The female victim was later transferred to Pamela Youde Nethersole Eastern Hospital for additional treatment.

"The male victim, found unconscious by firefighters, was also treated promptly and taken to Pok Oi Hospital, where he was pronounced dead."

The incident prompted the evacuation of over 400 residents from the building.

The Fire Services Department said preliminary investigations indicate the blaze originated in the living room.

Assistant Divisional Officer Chow Tsz-ho said a response team was deployed in the aftermath to inspect the building's safety measures.

"After the fire, the response team tested the building's fire safety equipment and found everything to be normal," he said.

He also confirmed the building holds a valid annual fire inspection certificate.