The Enforcement Directorate has filed charge sheet against 4 telecom firms for FEMA violation involving 4,300 crore rupees in 2G scam case. PTI quoting sources says, the Directorate has named Swan telecom, Loop Mobile, Loop Telecom and S-tel in its charge sheet filed in Delhi court. The Dirctorate also suspected FEMA violation by Virgin Mobile, a Tata joint venture and analysing pricing issue of shares between Unitech and Telenor. The Directorate said it is looking into cash guarantee issued to Sistema. It says, investigation under FEMA has revealed 'large scale' contraventions by telecom companies and their associates in the 2G spectrum allocation case.