Builder absconding without completing the building

Sir, I booked a 2 BHK flat at kolathur in chennai during May 2013. It is a four flat building in 2400 sq.ft. Actually, the builder (Aura Deziner Builder, Chennai) has entered into an agreement (JV) with the land owner, such that 2 flats is for the land owner and 2 flats will be sold by the builder. As per my agreement with the builder, the flat has to be handed over by Jan 2014 with a grace period of 3 months. Both the flats have already been booked during 2013 itself. But the flat is still not completed. Only Ceiling work, wall plastering, front elevation, staircase work are completed so far. Electrical, plumbing, tiling, common area work, terrace tiling, other amenities are still pending. It is a G+2 flat (Gr flr - 1 flat, 1st flr 2 flats and 2nd flr 1 flat). Individual car parking, gym and visitors lounge are also in the agreement. The builder at different times has said that he is having some financial problem and he has applied for a loan with 3rd party collateral. He was telling that for about an year. For the construction work he has already got more than 90% of the payment. Every time we the flat purchasers meet the builder, he used to stay that by the end of this month or by next month he will start the work. And at some times to complete particular part of work he used to get money from us itself. But, now for the past 20 days, he could not be contacted over phone or in person. His office staff are also not knowing his whereabouts. Another person his close associate (or his partner) is also not knowing his whereabouts. It seems that he has obtained lot of loans and now his partner is become answerable for all the loans. But now the person is telling he is not the partner and is only the employee of the company and looking after execution of the projects of the company. Please guide me how to proceed. Now the land owner who has entered into an agreement with the builder for joint venture has also in need of the flat met myself and the other purchaser and discussed whether there is any possibility of taking over the site and we ourselves can build the flat. But nobody knows about the legal procedures how to take over and if possible how to recover the money from the builder at a later date. Please guide me how to proceed.