Hassle in Sale of flat

Sir/Madam, I am the second owner of a flat in a CHS. My housing loan is from ICICI. All my original property docs are with ICICI. The share certificate is in our name. Recently i sold my flat recently. When it came to issue of NOC by the society, the society informed us that they received a letter from the HSBC bank that they had given personal loan to the first owner of this flat for which the owner had mortgaged the flat. Now we have been living in the flat for the last 6 to 7 years. We had put a notice for sale on the society's notice board but the society never informed us that they have an issue. The first owner was issued NOC by the society at the time we purchased the flat from him. Now when we are asking for NOC from the society, they are telling us that they are going to mention the case of the HSBC letter on the NOC. Now when it is not our fault and the society has shown its negligence in taking appropriate steps and informing us, why should we be the victim of someone else's fraud. And all the original papers are with ICICI and we have also cleared the loan and they are going to issue the foreclosure letter. Please advice what should we do. We need two NOCs from society and the society is delaying the issue of NOC as per the required format. We have bought the flat in good faith and had HSBC been in the possession of any documents, they would have taken possession of the flat as of now. we never received any intimation from HSBC for any dues. Is there any legal way out. Request you to reply on an urgent basis as it is delaying the entire process.