Two expert witnesses have countered the government's argument over the cause of the fatal collapse of a 55-year-old tenement in To Kwa Wan, with one of them saying officials should have evacuated the building months before the tragedy. The two structural engineers, testifying on the fifth day of the inquest into the cause of death of the four killed in the incident, disagreed with the Buildings Department's view that a repairman who was clearing illegal structures hours before the collapse should be held responsible. The experts were invited by police to investigate after the block on 45J Ma Tau Wai Road crushed four people to death, in January last year. Eddie Lam Siu-shu, a professor of civil and structural engineering at Polytechnic University, said the tenement building was 'very dilapidated' and that three structural columns of the block were 'dead years before the collapse'. His statements were based on findings from laboratory tests and analyses of debris samples. '[If I think] from the government's point of view, the block should have been declared a dangerous building, and a closure order should have been issued,' he said. Earlier in the inquest, a frontline surveyor of the Buildings Department, who inspected the site two months before the collapse, told the court that he did not then consider a closure order was necessary since he thought there was no immediate but only 'potential' danger. Lam also said the quality of columns' concrete was substandard, with many pores and not enough water added during manufacturing. Another expert witness, Greg Wong Chak-yan, former president of the Institution of Engineers, said he did not agree with a Buildings Department engineer who testified on Thursday that Chu Wai-wing, the repairman, hired by block owner Chak Oi-luen, should shoulder the blame. The government engineer had said work had disturbed beams and columns and started a chain effect ending in the collapse. Wong said Chu had had only a 'very minor' role in causing the collapse. 'Chu was only using a hand-carried electric saw that would cause, compared with other equipment we use, minimal vibrations in the beams and columns,' he said. 'I have different views from the [government engineer] maybe because he's a law enforcer and I'm a consultant ... I don't feel I should say in such a tone that someone made a big mistake just because he made a few shakes.' He agreed with coroner Michael Chan Pik-kiu's description that Chu's action was 'the last straw that breaks the camel's back'. He said he believed a column at the shopfront corner, rather than the one near where Chu was working, was the first to fall and trigger the collapse, judging from witness statements and a photo taken by a passer-by minutes before the incident, which showed two cracks developing on the front. Long-time lack of repair and erosion by rain and water seepage contributed to the column failure, he concluded. The inquest continues Monday.