Hong Kong  - An investigation was underway in Hong Kong Monday following a fire in a 15-storey building which left four dead and at least 55 people injured.

The blaze - one of the worst in the city in the last decade - began in a karaoke nightclub on the mezzanine floor of the building early Sunday morning and spread upwards through the high-rise block of flats trapping dozens of residents.

Those dead include two firemen whose bodies were recovered from the 12th floor of the block in the city's densely-populated Mongkok district, a fire services spokesman said.

A woman resident aged 77 also died after being taken to hospital and the charred body of an unidentified fourth victim of the blaze, believed to be female, was later found in the building.

At least 55 people were injured in the fire that raged for six hours. Twenty-two people were admitted into hospital, of which three men and one woman were said to be in a serious condition Monday.

More than 200 firefighters were involved in the rescue operation bringing more than 90 people to safety.

The alarm was raised by a nightclub hostess at around 9:30 am who described hearing a loud bang followed by clouds of smoke which quickly engulfed the corridors of the building.

Firefighters claimed the rescue operation was hampered by intense heat and heavy smoke trapped in the narrow corridors of the building.

The two officers who died were a 46-year-old senior officer and father-of-one who had been with the Fire Services Department for 26 years, and a recent recruit aged 25, who joined only last year.

A Fire Services Department spokesman the cause of the blaze was not thought to be suspicious but said they would investigate if there were any violations of fire regulations which may have helped the blaze spread quickly.

Residents claimed illegal structures within the building had made it a death trap. (dpa)