A businessman yesterday died of injuries he suffered in a blaze which tore through an office block in Wan Chai on Thursday. Wa Yeung, 33, chief operating officer of hi-tech company Biztech, died in Ruttonjee Hospital after being found unconscious on the 16th floor of the building. He had been with the company for less than a month. The fire broke out in the Shanghai Industrial Investment Building in Hennessy Road at 9.20am on Thursday. Three people were critically injured, including Wa, and another four, including a fireman, suffered smoke inhalation. About 120 office workers, including shipping tycoon George Chao Sze-kwong and his staff, were trapped on the roof of the building for more than two hours. The office block, which does not have an automatic sprinkler system, is one of 550 older commercial buildings which are supposed to upgrade their fire safety facilities under laws introduced after the 1996 Garley Building fire in Nathan Road, which killed 40 people and injured 80. The Fire Services Department was unable to confirm claims by some evacuees that some of the fire doors in the building were locked. Officials dismissed allegations they had been slow in checking the old buildings. Acting Chief Fire Officer (Headquarters) Chu Man-chun said his department had inspected 378 of the 550 buildings. He said the department was ahead of its planned target of 140 buildings a year. 'It is unrealistic to require owners and occupiers to improve their premises overnight because there are commercial activities going on in there,' Mr Chu said.