Hyderabad: Shadow teams constituted by the Greater Hyderabad Municipal Corporation (GHMC) have revealed that over 70 per cent of the ground-level staff indulge in corruption and even threaten the residents if they refuse to pay the bribes. A senior town planning official on request of anonymity said a report submitted by the shadow teams had divulged that ground-level officers were hand in glove with the builders and have been wrongly assessing the properties and not even identifying the unauthorised structures. The sources told The Hans India that the ground staff, which includes building inspectors and section officers, has been causing a dent of about Rs 500-crore revenue to the GHMC. It may be mentioned here that the GHMC had constituted the shadow teams in all the 30 circles following building collapse at Nanakramguda and the railing collapse at Chandralok Complex. The sources said the GHMC had now instructed deputy commissioners to identify the number of ongoing unauthorised constructions and dilapidated structures which are more than 30-year-old. The sources said the corporation was examining various options that are available to initiate action against the corrupt officials. One of the ways is to demote them. The GHMC can sack the outsourcing employees if found corrupt, but it cannot do so in the case of the regular employees. The officials said that they would take up the matter with Municipal and Urban Development Minister K T Rama Rao.