Top firms include Tata Steel, Sterlite Energy, GMR Energy. The Union government has threatened to cancel coal block allocations of as many as 17 companies for failure to develop those allotted to them years before. These include big companies such as Tata Iron and Steel, Sterlite Energy, GMR Energy, ArcelorMittal India, Reliance Energy, GVK Power, Lanco Group and Rungta Mines. The ministry has issued separate showcause notices asking the reasons for the delay, to be replied to within a month. The notices, served on November 3 and 4, ask why the delay should not be held as violation of the terms of allotment and in case of delay in replying,