MUMBAI: Even as a team of Mumbai police officials left port waters to bring in the captain of the merchant vessel involved in Sunday's collision for questioning, the Indian Navy started operations to retrieve the partially sunk INS Vindhyagiri. The frigate had caught fire after a collision with a merchant vessel MV Nordlake on Sunday. Captain Manohar Nambiar, chief public relations officer, Defence, said: ''Our first priority is to pump out oil from the tank and also water that has entered the compartments of the ship. Once this exercise is complete, the weight of the ship will reduce. The vessel will become lighter and hopefully it will become upright.'' The collision had left the frigate crippled and tilting in about seven metres of water in low tide at the naval dockyard. The Navy has yet to take a decision on whether to repair the 29-year-old frigate, which is due to be decommissioned in a year or two. The priority, said officials, is to ascertain the extent of the damage and the exact cause of the fire.