HONG KONG -- Five firefighters on Sunday remained in a critical condition in hospital following Saturday's gas explosion in Hong Kong's Kowloon, which left one person dead and 12 others injured, according to the local government.

Nine of those hurt in the blast were firefighters. They were paid a visit by Chief Secretary Carrie Lam on Sunday afternoon.

Lam stressed the government would provide them with all necessary assistance.

Director of Fire Services Lai Man-hin said a special investigative committee was beginning to look into the cause of the explosion and what led to the multiple casualties.

The police earlier said the man who died in the explosion, a resident in the building, could have suffered from mental health problems.

The explosion took place near midday Saturday in a flat of Mei Ying House in Kowloon's Shek Kip Mei Estate. Witnesses said smoke came out of a flat's window while broken glasses lay on the ground below. A number of victims were taken to hospital by ambulance, including firefighters.