Issue with regards to backyard Shaft area

We have recently bought a flat in a building in Shalimar Garden Extension-1 Sahibabad Ghaziabad. The house is still undergoing renovation. The labour has gone to their village for a month and hence, the house is closed from past 3 weeks. The house is at 1st floor with nothing on ground floor. The backyard Shaft area is open and is divided between 4 flats on the same floor. There used to be a common drainage line in the area which helped drain rain water. Later, one of the flat party built a wall to segregate their area and the other party built a small dividing line with bricks to segregate their own area and also captured the common drainage. Now, due to these segregation, the third party built a drainage line of their own in their side of the Shaft area. Recently, there was a water logging in our side of the drainage area due to continuous rain. One of the neighbor called us and asked us to clean. We were waiting for our labour to come back and told them that we will get it cleaned as soon as they come back. Since the neighbour was impulsive and impatient, he filed a complaint in nearby police station for the same. Now, they are asking us to build a separate drainage line in our side of the Shaft area which we are contesting. I want to understand what is the role of police here as this should be a Ghaziabad municipal corporation matter and also that the 15k expense should be borne by all the floor residents as this is common property and not even mentioned in our title Deed. I also need legal advise as to what can those neighbour do and how can we avoid police interference in this matter