Is modification in the villa property illegal?

We have recently purchased a villa in Bangalore which comes with additional land being as this being a corner unit at the dead end. Every villa has an individual Khatha and plan has been sanctioned by BDA. We started the work for extending living room and kitchen without touching the elevation. While putting the foundation, we figured out that there are things belonging to common infrastructure running underneath our property. This is the case also with other units. Association has put our work on hold and is telling us not to do any structural changes as it can damage the common infrastructure also citing legal issues with regards to structural changes in the existing plan. Can association stop an individual from doing such renovations? What actions should I take in case the association doesn't agree? Is it illegal to do modifications in a gated community like villa or row houses? Can I take an approval from BDA ? Can I legally ask Association or Builder to remove