The city's air quality remained in the upper level of the 'very poor' category on Thursday with an air quality index (AQI) of 388 at 11am and 390 at 4pm. AQI is predicted to slip into the 'severe' zone by Saturday.

Despite a slight improvement over Wednesday's 395 due to better wind speed, several areas in the city recorded a "severe" AQI.

According to the Indian Institute of Tropical Meteorology's Air Quality Early Warning System, AQI is likely to be 'very poor' on Friday, and may turn 'severe' by Saturday. For a week since Sunday, it is likely to stay in the 'very poor' zone.

Some of the areas in Delhi that recorded 'severe' AQI were Bawana (445), Jahangirpuri (436), Vivek Vihar (434), Alipur and Punjabi Bagh (426), Nehru Nagar (425), Vivek Vihar (424), Rohini (423), Sonia Vihar(422), Mundka (419), RK Puram (413), Okhla Phase-2 (407), Narela and Patparganj (403), and Dwarka Sector 8 (402).

With the harvest season in Punjab almost concluding, incidents of stubble burning are declining, making local pollution sources responsible for the capital's air quality.

On Thursday, satellites detected 205 paddy residue burning events in Punjab against 512 on Wednesday, taking the total number incidents in this season to over 36,000. In Haryana, 23 incidents were reported and 307 in Uttar Pradesh.

According to the forecasting body Decision Support System, the share of biomass burning that incorporates stubble burning in Delhi's PM2.5 was estimated at around 8%, while 13% was the share of transport and 42.6% of other sources.

According to the Central Pollution Control Board, the PM2.5 level at 4pm hovered around 203.9 micrograms per cubic metres and the PM10 level at 353.2. Environment minister Gopal Rai said the GRAP-3 restrictions would continue.