Delhi and the National Capital Region on Thursday woke up to a thick smog the morning after Diwali celebrations in the region. The Air Quality Index in the city was the worst of the season so far, at levels beyond “severe” the entire day, according to the Centre-run System of Air Quality and Weather Forecasting And Research, or SAFAR. The index was at 642 at 4 pm. Values between 401 and 500 on the index are categorised “severe”.

The index given by the Central Pollution Control Board, which calculates the 24-hour average data, showed the figure at 325 at 6 am, which worsened to 379 by 3 pm. Both these values lie in the “very poor” category, which poses a risk of respiratory illness. As the day progresses, this index, too, is likely to show higher values, as it will capture more parts of Thursday in the 24-hour period.

The surge in pollution level was caused by bursting of firecrackers on Wednesday, leading to the formation of a smoky layer across Delhi-NCR, authorities said.

There were several violations of the Supreme Court order on firecrackers, with people bursting fireworks outside of the two-hour limit mandated by the court. The court had also instructed that only “green fireworks” be burst between 8 pm and 10 pm on Diwali. Violations of the order were reported from across the NCR – at Mayur Vihar Extension, Lajpat Nagar, Lutyens Delhi, IP extension, Dwarka, and Noida Sector 78 among other places, according to PTI.

The Delhi Police have registered 562 cases under Section 188 (disobedience to order promulgated by a public servant) of the Indian Penal Code in connection with bursting of firecrackers and initiated legal action against 24 juveniles, The Indian Express reported. The police also registered 72 cases under the Explosives Act and arrested 87 persons for the illegal sale of crackers.

The Capital experienced severe air quality on Monday, likely due to stubble burning in neighbouring states. Analysts, however, predicted a further decline this week post-Diwali. “Air quality will be bad on Thursday and start to improve from Friday even if partial toxic crackers as compared to 2017 is burned,” SAFAR had said. Stubble burning in areas near the national capital is also adding to the pollution, the agency added. It also predicted that the PM10 concentration in Delhi will reach 575 and PM2.5 will be 378 on Thursday if crackers are burst.

The pollution authority could also consider inducing artificial rain after Diwali to wash away hazardous pollutants.