Families of the six workers killed when a work platform plunged 20 floors down a lift shaft at the International Commerce Centre want a monument to pay tribute to the men and remind people about the importance of industrial safety. After meeting Labour Department Commissioner Cherry Tse Ling Kit-ching yesterday, they said they had asked that the message be conveyed to developer Sun Hung Kai Properties. 'We hope Sun Hung Kai will build a monument in remembrance of the incident. It would be a symbol of their contribution and a reminder to citizens about how important industrial safety is,' a son of victim Hui Chi-kwong said. Sun Hung Kai Properties did not respond to a request for comment. The families also voiced their discontent after labour chief Matthew Cheung Kin-chung said the investigation into the incident would take six months. 'Everyone wants to find out the truth. Six people were killed. The investigation must be speeded up,' Hui's son said. Ip Wai- ming, of the Federation of Trade Unions, who met labour officials with the families, said Tse had said the inquiry might take less time. Tse said the department would help the families seek compensation and ensure investigators got to the bottom of what happened. 'We also pledged to finish inspecting lift shafts in similar projects before mid-October in a bid to prevent a repeat of the tragedy,' she said. Police, meanwhile, said autopsies could not conclude the cause of death and further examinations were required. The Housing Department said safety measures had been implemented after a worker was killed by a falling object in a lift shaft at a West Kowloon public housing block in 2004. Terry Ching Lam Kwai-chun, a senior manger at the department, said it was forbidden to throw waste down a shaft and gates had to be installed on every floor. Safety nets were required every 20 metres and if a work platform was built, a supervisor must be assigned.