Commission for Air Quality Management (CAQM) on Monday invoked Stage II of Graded Response Action Plan (GRAP) across Delhi-NCR ahead of Diwali. The move comes as Delhi's air quality deteriorated to 'very poor' category, with AQI reaching 324 at 4 pm today. Under GRAP Stage II, authorities are required to step up anti-pollution measures and encourage the public transport's use.