Property accquired in mortgage

We live in a 50 year old building, a part of which was given to a bank in exchange of a loan taken by the landlord from them. The landlord hoped to pay back the bank and re accquire his property. But this did not happen and the bank continues to occupy the property till date ie since past 50 years. The building has three other tenants besides the bank which occupies 12 remaining flats. The original landlord of the building has passed away and all his children are abroad or basically non traceable. The building is in a very poor condition and in urgent need of repairs. What is the banks legal status with respect to property after 50 years. If we approach the bank for looking into the repairs they say that their stand is that this being rental property they are not willing to spend on repairs. Can you guide me on how I can convince the bank to undertake repairs