The fire brigade chief has expressed regret that his senior officer's defence of the rescue operation during last week's fatal blast at a Wong Tai Sin estate upset victims' families. Director of Fire Services Hsu King-ping made the remark in a letter to the families of the two mothers killed in the explosion after he was urged to clarify the department's comments. Secretary for Security Regina Ip Lau Suk-yee also wrote to the victims' families to clarify her remarks and express her condolences. But the victims' children say neither answered their questions directly and that Mr Hsu wrongly concluded that their mothers died in a fire. The explosion, which occurred at a 15th-floor flat in Tsui Chuk Garden last Wednesday, killed three women and injured 21 people. Both Mrs Ip and Mr Hsu said afterwards rescue workers had followed normal procedures when breaking into the gas-filled flat. Mr Hsu said the blast was not sparked by their breaking in as it happened after they had entered the flat, contradicting residents' accounts. Kowloon's deputy chief fire officer, Chan Yun-pui, earlier said officers sprayed water to avoid igniting the gas while trying to break into the flat. But witnesses later said this was not true. In his letter, Mr Hsu said Mr Chan's comments had been made in reply to media inquiries, and that a taskforce had been set up to probe the incident properly. Lam Po-hung, 37, son of victim Ngan Hau-lan, 75, said he believed his mother had died in the blast, not the fire. 'I want to see justice done for my mother. She has been deprived of her right to live. No one should be deprived of such right,' he said. Liu Ming-yiu, 26, son of the second victim, Sze Chui-ngor, 51, added: 'Their letters did not answer our questions directly. My mother was not burnt to death. The doctor said she died of internal bleeding.' Mr Lam and Mr Liu said that 13 households made homeless by the blast and temporarily accommodated in public flats were dissatisfied that they had been asked to pay rent. A Housing Department spokeswoman said it was not policy to waive rent.