BARMER, July 8 -- A land subsidence led to deep sinkholes and long surface cracks near Mangala Well Pad-7, which is part of India's largest onshore oil production site in Barmer district, raising alarms, officials aware of the matter said on Monday. Police found that cracks have been formed along a stretch of about 250 metres, with deep pits appearing in multiple spots. Station house officer (SHO) of Nagana police station Jameel Khan said that a local resident, Prema Ram, informed police about the development, following which Nagana police reached the spot and alerted the officials of Cairn Oil & Gas, the company that operates the well pad. SHO Khan said, "Both the company officials and administrative authorities have been informed." Company representatives visited the site and have summoned a geological survey team from Jodhpur to investigate the cause of the subsidence, officials said. Preliminary probe suggested that the cracks and sinkholes could be a result of underground disposal of waste materials generated during oil production, or possibly due to underground blasting. However, the exact cause will be determined after the survey team completes its investigation, officials added. Police have advised villagers to stay away from the area, and the authorities have planted red flags around the sinkholes....