Twenty people have been arrested by ICAC officers over the past three days for their alleged involvement in substandard piling work at two housing blocks in Tin Chung Court, Tin Shui Wai. The operation was mounted after a complaint from the Housing Department. Excessive tilting at one of six Home Ownership Scheme blocks was not detected until the building had been finished, prompting the department to suspect corruption in the concealment of substandard work. Those arrested include five on-site staff from the architectural consultant appointed by the Housing Department - a project structural engineer, a resident engineer, an assistant clerk of works and two supervisors. Also held were two directors of the piling contractor and nine of the firm's staff - a contracts manager, two quality control engineers, a site agent, three pile designers, a registered structural engineer and a foreman - as well as a subcontractor who provided labour for piling works. A senior structural engineer and a structural engineer from the Housing Department responsible for supervising the consultant in relation to the project and an engineer of the geotechnical sub-consultant were also among those arrested. All were released on bail as the Independent Commission Against Corruption continues its probe. ICAC inquiries revealed the arrested staff might have manipulated pile design calculations in two of the blocks and falsified data to mislead an architectural consultant into believing that the designed pile length would meet specified engineering criteria. Inquiries also suggested that records on the length of the piles might have been falsified. Examination of some installed piles revealed that a number were short by at least one metre. The ICAC alleged some of the on-site staff from the architectural consultant had received free entertainment from the piling contractor, including meals and visits to nightclubs. In return, they were allegedly lax in supervising the project. The Housing Department barred the senior structural engineer and the structural engineer in accordance with civil service regulations after their arrest. In a statement released yesterday, the department said: 'The department takes the case most seriously and will continue to offer full co-operation to the ICAC.' After discovering excessive uneven settlement at the site in September 1999, the department alerted the ICAC and appointed an independent structural consultant to assess the condition of the blocks and propose remedial measures. The Housing Authority had agreed to remedial works and its legal representatives were examining various legal options against the parties involved to recover the loss and damages it suffered, the statement said. It said the department had now set up a high-level anti-corruption committee. Chaired by the Director of Housing with ICAC representation, the committee will strive to reinforce a culture of integrity among staff.