3rd floor construction

Hi I stay in builder apartment in chander nagar. G+2 floor with a basement covering 50 percent of plot size. It does not have a stilt parking. Recently person having roof rights have started building 3rd floor . In our locality or any anywhere in ghaziabad 3rd floor is not constructed until you have 100 percent stilt parking. Since the builder is not reachable we are unable to check how did he get a possesion to build 3rd floor. What should we do in order to check whether the construction is illegal or does property rule allow you to build 3rd floor . Regards Achin Thakur