The government has intensified its drive against the firms sitting idle on coal blocks. The Coal Ministry has asked companies to give status report on the development of captive blocks allocated to them for the April-June quarter. It has also started issuing warning letters to firms asking them to either begin production of the blocks or see them being taken back. Last month, the Ministry took a decision to de-allocate 14 coal blocks and one lignite block and to issue warning to 29 coal and 3 lignite allocatees asking them to commence production in time. AIR correspondent reports that since last month, the government has de-allocated coal blocks of companies like NTPC, Andhra Pradesh Power Generation Corporation, Jharkhand State Electricity Board, Damodar Valley Corporation and Gondawana Ispat Ltd.