New Delhi: The capital witnessed the most polluted day of the season on Monday with the air quality index (AQI) recording 434, which is equivalent to the 'severe plus emergency' category. 

What was more dramatic was that, on Sunday, the capital recorded the cleanest air in November in the past three years. 

The PM2.5 (particles in the air with a diameter of less than 2.5 micrometres) and PM10 concentrations touched 365 and 503 respectively, touching the 'severe-plus emergency' category, according to Central Pollution Control Board (CPCB) data.

In NCR, Faridabad, Ghaziabad, Noida and Greater Noida recorded "severe" pollution levels while Gurgaon recorded "very poor" air quality, CPCB data showed.

Experts believe that the condition worsened due to a drop in temperatures, a rise in moisture levels and related meteorological conditions. 

CPCB chairman SP Singh Parihar said the deterioration of the air quality will continue till Tuesday morning.

"But the good news is that speed of surface wind has improved, which may help in dispersing the pollutants," he said.

An official of the Centre-run System of Air Quality Forecasting and Research said intensified stubble burning is contributing nearly 24 percent of the air pollution in Delhi.

Another official said if the air quality continues to remain in the "severe" category for 48 hours, they would consider implementing more regulations.

The Indian Institute of Tropical Meteorology said biomass burning is also contributing to the spike in PM2.5 concentration.

The increase in pollution levels comes despite strict control measures imposed by the government in Delhi.

It has launched an aggressive 10-day 'Clean Air Campaign' from November 1 to monitor and report polluting activities and ordered halting of construction activities and regulating vehicular traffic.

Civil construction has been suspended in Delhi and surrounding areas of the National Capital Region. All stone crushers and hot mix plants generating dust pollution have also been closed.

The Delhi Pollution Control Committee has directed the transport department and the traffic police to intensify their drive against polluting vehicles until November 10.

Union Environment Minister Harsh Vardhan on Monday said no leniency would be shown to those violating pollution control norms.

He again warned that legal action was being initiated against people violating the regulations.

Delhi Chief Minister Arvind Kejriwal has said stubble burning in Punjab is the main reason behind the current cycle of air pollution in Delhi.

On Sunday, Punjab Chief Minister Amarinder Singh termed his claim as "nonsense".

But satellite images by NASA on Monday showed a large number of farm fires in Ludhiana, Jalandhar, Sirsa and other areas of Punjab and Haryana.

Enforcement data provided in response to an RTI query by activist Deepak Juneja has shown that despite the Delhi government deregistering 40 lakh old petrol and diesel vehicles to curb air pollution, only 3,196 vehicles have been impounded, which is less than 1 percent of the total.

With inputs from PTI