A total of 44 fire engines and 210 firefighters were sent to tackle the blaze, with 26 ambulances called.

One of those injured in the blaze, which broke out early yesterday after hawker stalls caught fire, was an 11-month-old baby.

Anna Tsang Yim-sheung, police deputy district commander for Mong Kok, confirmed the blaze, the city's deadliest for 15 years, was being treated as suspicious.

She said: 'We will consider all the clues. This is a very serious offence. We will try our best and use all our resources to investigate the crime.'

Suspicions were raised when it was discovered that two booths at the opposite ends of Fa Yuen Street had caught fire simultaneously.

One police officer said inquiries also revealed there had been an argument in the street. He added: 'We are investigating whether it [the argument] is linked to the arson case.'

It is the second fire in Fa Yuen Street in a year. Last December, stalls caught fire leaving six injured and leading to the evacuation of 200 residents. Police last night named three of the dead as a woman, Chen Xianxian, 24, and two men, Choi Wai-ming, 51, and Ng Kui-mau, 63.

A fire officer who discovered some of the bodies said: 'They were blackened, either from severe burns or because they were coated with black smoke.' He said it appeared most died from smoke inhalation.

Along with the baby, 16 men and 17 women aged 20 to 75 were injured, of whom five are in critical condition.

The fire broke out at 4.40am and was under control at 11.11am. It was largely extinguished at 12.28 pm by 12 teams of firefighters equipped with breathing apparatus.

Kowloon's acting chief fire officer, Szeto Yat-san, said: 'When we arrived, the fire was very serious. Over 30 residents called for help.

'We had to deploy some of the officers for a rescue operation. We needed a large number of colleagues in a short period of time, so we upgraded the fire alarm to category three and four afterwards.'

He added: 'We need to investigate why so many casualties were caused by the fire.'

The death toll is the worst since the handover. It is exceeded only by the Garley Building fire in Jordan in 1996, which left 41 dead and 81 injured, and the January 1997 arson attack on Top One Karaoke in Tsim Sha Tsui, in which 17 died and 13 were injured. Official documents filed with the Land Registrar show that in June last year, inspectors declared that buildings in Fa Yuen Street through which the fire swept were 'liable to become dangerous'.

The owners were ordered to carry out repairs and maintenance by December but the records do not state if the work, on 188 and 196 Fa Yuen Street, was carried out.

Fourteen of the injured, including the baby, went to Kwong Wah Hospital, with 13 going to Queen Elizabeth Hospital and others to the Princess Margaret and Queen Mary hospitals.

Edward Leung Wai-kuen, vice-chairman of Yau Tsim Mong District Council, said poor building management had increased fire hazards in the neighbourhood, with many blocks in Fa Yuen Street lacking fire doors and security guards.

'If they had hired a guard to monitor safety, the number of deaths could have been reduced,' he said.

Chief Executive Donald Tsang Yam-kuen expressed sadness and shock after visiting some of the injured in Kwong Wah Hospital.

He said: 'Last year there was a fire in Fa Yuen Street. It was discussed in the district council.

'We have taken measures to separate the booths from the residential blocks. We have also restricted the amount of stock stored [in stalls] and expansion [of stalls].

'We have done all these things. But apparently they are not enough. We need to review these measures to prevent any similar incidents.'

A government spokesman said Tsang had directed the chief secretary to lead an inter-departmental working group to co-ordinate efforts after the fire, including the provision of relief to affected families as well as actions to enhance public safety.

Secretary for Security Ambrose Lee Siu-kwong expressed sympathy to the victims' families after visiting the scene with Director of Fire Services Andy Chan Chor-kam.

Police want anyone with information to contact them on 9022 0072. To inquire about the injured, the public can call a police hotline on 2398 6329.