Leakage from the top of my flat.

We live in a trust building in Mumbai and have living there since 1983 and the buildings constructed in 1935. For the past three years there has been leakage into our flat from the ceiling and other areas. These visible leakages are no longer present. Leaks have commenced from 2019, ever since the present tenants commenced modifications to the original plans of the flat. The changes were as follows; 1. A bathroom cum toilet was erected on top our kitchen. 2. The toilet was demolished and a kitchen constructed in its place. 3. Insertions were made into walls and doors fitted. Our complaints to the tenants living above us went unheeded so in 2020 we complained to the Trust and requested them to advise those tenants to rectify the source of leakage that had soiled portions of our kitchen ceilings and walls An inspection was carried out by an appointed repairer on / around 6th March 2020, wherein those tenants were verbally advised to rectify the leakage from their bathroom/toilet enclosure. On our return to Mumbai in January 2022 it was noted that the patches had increased in dimensions and the Trust was informed about it in the first week of February. We informed the Trust that those leaks were due to the modifications carried out by the tenants above but it was strenuously refuted by the Trust via email and their contentions were that the structural integrity of the building or structure was unaffected. An inspection, by a qualified individual appointed by the Trust of our flat and damage was carried out end April, that was in conjunction with a survey of the structural integrity of all four buildings owned by the Trust. Further the tenants above were advised to carry out a leakage test from the drainage which they have done and video taped. Today the Trust sent us an email stating that due to the leakage from our flat the structural integrity of the building was getting compromised and to carry out damage mitigation in cooperation with the tenants above and share. The tenants above also claim that the leakage were due and exacerbated due to the monsoons which oddly upto the present time have been absent. Please note the following, 1. Leaks were first noted in 2019. 2. Photos of the leaks were taken in February 2020 and February 2022. 3. We have photographic evidence - February 2020- of water droplets at the exact mid centre of our ceilings, which is no way exposed to the external elements. 4. Leaks have only commenced since the modifications on the top flat was carried out. From 1983 to 2019 ther were no leaks. 5. Our request for assessing any plans of the modifications have not been addressed. We are unsure of how to proceed as we feel the Trust is biased against us. King advise us on what course of action to take.