The National Green Tribunal, NGT, today questioned the Centre as to why no environmental clearance is required for erecting structures in Yamuna flood plains for Sri Sri Ravi Shankar's Art of Living World Culture Festival. A bench headed by NGT chairperson Swantanter Kumar asked Ministry of Environment and Forest to file an affidavit by tomorrow and tell why no environmental clearance is needed for raising temporary structures. <br/><br/>The direction came after counsel appearing for the Ministry said that they have found no debris at the site, when an expert team had visited and as per Environment Impact Assessment notification 2006, no environment clearance is needed for temporary structures. The Green Panel also questioned the building up of pontoon bridge by the Army on river Yamuna for the festival, and asked the Delhi Development Authority (DDA) counsel as who gave the permission for setting it up.