A construction workers' union has urged contractors to step up safety inspections at construction sites. The call follows an accident on Tuesday in which two 6-metre metal pipes fell more than 30 floors at a North Point construction site, landing on the street below and damaging eight vehicles. A third pipe landed on the canopy of the building under construction. 'Contractors should make sure lifting of heavy construction materials is handled by experienced workers only and make sure workers employ every safety measure. Inspections should be more frequent,' Construction Industry Employees' General Union chairman Choi Chun-wah said. Mr Choi said all workers who were in charge of lifting heavy construction materials should undergo training and attend courses before they were allowed to do the job. 'It takes years of experience and skill to do the job well or else heavy materials like metal pipes will fall on busy streets just as it did at the construction site in North Point.' The union is planning to hold a training course for workers. 'We held a two-day course last year and we gave out certificates to 1,500 workers. These workers are very important in the construction industry, as most buildings in Hong Kong are high rise and lots of construction material have to be lifted to upper floors,' he said. Mr Choi said Tuesday's incident was probably caused by the lack of safety awareness. 'I suspect that everything was okay when the pipes were being lifted and problems arose when workers tried to unload the pipes,' he said. But legislator Patrick Lau Sau-shing, who represents the architectural sector, said supervision was difficult as safety consultants could not follow every worker all the time. Four construction workers, arrested on Tuesday at the North Point site, remain on bail. Investigations into the incident are continuing.