20 of the 37 air quality monitoring stations recorded pollution levels in the "very poor" category.
Days before Diwali, Delhi's air quality plunged to "very poor" category and was in the "severe" category in Mundka, one of the 14 pollution hotspots in the city, owning primarily to unfavourable wind speed.
Twenty of the 37 air quality monitoring stations recorded pollution levels in the "very poor" category.
While the monitoring station at Mundka recorded the air quality index at 428, which falls in the "severe" category, Anand Vihar recorded AQI of 390, Wazirpur 363, Jahangirpuri 359, Rohini 356, Dwarka sector eight 351 and Bawana 346.
AQI in the neighbouring towns of Baghpat, Bhiwadi, Ghaziabad, Greater Noida, Gurgaon, and Noida was 314, 312, 346, 327, 310 and 328 respectively.
An AQI between 0 and 50 is considered "good", 51 and 100 "satisfactory", 101 and 200 "moderate", 201 and 300 "poor", 301 and 400 "very poor", and 401 and 500 "severe".
The Ministry of Earth Sciences' air quality forecast and research service, SAFAR, said: "The overall air quality of Delhi is in the "very poor" category. The decrease in wind speed has started to negatively influence Delhi's air quality by drastically decreasing ventilation coefficients and thereby effecting dispersion."
"The fire count in northern India has reduced slightly but is still moderate at 700. However, winds in the boundary layer, where biomass intrusion takes place, are not quite favourable to influence Delhi''s air quality significantly for the next two days."
Calm surface winds will continue for the next two days. Consequently, the AQI is predicted to oscillate between high and middle range of the "very poor" category, it said.
The System of Air Quality and Weather Forecasting and Research (SAFAR) said another western disturbance is likely to affect the western Himalayan region by October 28. In view of this, the situation on Diwali may not be as bad as last year.
A 10-member task force on the Graded Response Action Plan said on Thursday that construction activities in Delhi and satellite towns of Gurugram, Faridabud, Noida, Greater Noida, Ghaziabad, Sonepat and Bahadurgarh will be banned between 6 pm and 6 am from October 26 to October 30.
During a meeting, the task force headed by Central Pollution Control Board Member Secretary Prashant Gargava also issued directions to close coal-based industries, barring power plants, in these satellite towns during the period.
"In Delhi, industries which have not yet shifted to piped natural gas will remain closed from October 26 to 30," it said and asked all implementing agencies to take strict action for checking stubble burning in Punjab and Haryana and ensure enforcement of the Supreme Court''s directions regarding firecrackers and impound "visibly" polluting vehicles.
Delhi Environment Minister Kailash Gahlot also asked the Delhi Pollution Control Committee (DPCC) to initiate prosecution against DDA''s vice-chairman if the urban body failed to remove construction and demolition waste from a 10-acre land near Karkardooma metro station by October 25.
The minister inspected the site located opposite G D Goenka Public School on on Thursday afternoon and expressed shock at the situation. The site is close to Anand Vihar, one of the 14 pollution hot spots in the national capital.
The minister said DPCC officials inspected the site on October 16 and issued a notice to the Delhi Development Authority (DDA) on October 22, asking it to remove the debris within 72 hours. "The land-owning agency is yet to initiate any action."
"I have directed the DPCC to immediately issue prosecution notice to head of the department, DDA (vice-chairman). At a time when pollution levels are rising due to stubble burning in neighbouring states, we cannot tolerate such things," he said.
The South Delhi Municipal Corporation said it has issued 10 challans amounting to Rs 21.35 lakh against polluters in its four zones on October 23.
While East Delhi Municipal Corporation issued 52 challans worth Rs 5.05 lakh on Wednesday, the North MCD challaned 214 polluters and imposed a cumulative fine of Rs 13.31 lakh on the polluters.