NEW DELHI: Timely action by flagship explorer ONGC on Friday averted a major environmental disaster off the Mumbai coast where a mile-long oil slick developed from a rupture in the company's undersea crude pipeline.Company chairman R S Sharma told TOI the slick was expected to disperse within 48 hours and estimated some 12,000 barrels of oil to have leaked. A statement issued by the company separately said the Coast Guard, after due assessment, withdrew the contingency plan since the "situation was under control''.The oil slick developed from a rupture in the Mumbai-Uran trunk pipeline that transports crude from the Mumbai High offshore fields. It was noticed at 8.45 am and the company immediately shut down the pipeline and stopped pumping oil from Mumbai High and Bassein oilfields.The fields were put back into production after three hours and crude oil is being sent through a separate line. The stoppage is expected to result in a production loss of 25,000 barrels. Mumbai High and Bassein fields together produce 247,000 barrels per day of oil.ONGC said the leakage was observed about two kms from the BPB Platform (Bassein oil and gas field) in western offshore. Contingency plans were immediately activated to contain damage to environment. Company vessels are keeping a watch on the slick and divers will be pressed into service to assess damage to the pipeline and repair it.Oil and gas production from Mumbai High is being diverted to the ICP-Heera Uran Trunk pipeline.