The National Green Tribunal (NGT) is investigating alleged illegal sand mining violations along the Yamuna River near the Delhi-Uttar Pradesh border. A joint committee reported that Nirmal Sand and Infra Private Limited conducted mining outside its lease area and during a period when such activities were prohibited due to air quality concerns. The committee also noted in-stream mining, unauthorized ramps, and excessive excavation. The NGT has given parties four weeks to respond before the next hearing.