How to deal with Unregistered flat association legally?

Sir We are residing in a flat association in Chennai which is run by unregistered flat association and maintaining a saving bank account in a PSU bank for past 20 years without KYC compliance. There is a secretary who has been embezzling funds in the name of association maintenance earlier his father in law was doing same. The flat perse has deviations and unauthorised constructions which the builder had committed in tacit connivance with one of the flat promoter who was awarded free flat for being partner to the crime. Now this promoter fellow is close to embezelling secretary of unregistered flat association. All flat owners of 13 flat building complex are also having flat deviations or have occupied common passage spaces in ground floor owing to their insecurities of having committed malfeasance they are all united in paying up to the secretary maintainance money as ransom. Both secretary and promoter of flats are drawing on the undue advantage of each flat persons crime and blackmail them also.The matter has gone to such extent many owners have locked up their flat and disappeared and many have despatched their children abroad to escape from Indian legal system. The only factor that keeps all owners united is monthly maintenance they transfer to savings bank account in PSU bank of the unregistered association We are the only flat owner fighting all of them tooth and nail and we want to take the matter legally head on with each owner.Kindly advice how to further proceed in this matter.We want to bring them to justice. Regards Satyaki Raghunath