The red dots indicate stubble burning in neighbouring states such as Haryana and Punjab.

The Delhi government shared NASA satellite images depicting "largescale stubble burning" in the national capital and its adjoining areas on Tuesday, a day when the region's overall air quality slipped to "very poor" levels.

In a letter to Union Health Minister Harsh Vardhan, Delhi Environment Minister Kailash Gehlot claimed that stubble burning in neighbouring states through November has "always contributed significantly to higher PM2.5 levels" in the national capital. The claim came a day after the Supreme Court-mandated Environment Pollution (Prevention and Control) Authority said that local sources of pollution in Delhi, Uttar Pradesh and Haryana are the primary reasons for poor air quality that plagues the national capital every winter.

Stubble burning is a post-harvest practice aimed at clearing fields. Despite a government-imposed ban, it still takes place in many parts of North India. However, satellite trends so far have indicated a marked reduction in instances of stubble burning in Punjab and Haryana this year.

News agency PTI reported the overall air quality index (AQI) of the region as hoving around 275 at 6:30 pm on Tuesday, while the neighbouring regions of Ghaziabad, Greater Noida and Loni Dehat inched past the 300 mark. An AQI ranging from 0 to 50 is considered 'good'; 51 to 100 is 'satisfactory'; 101 to 200 is 'moderate'; 201 to 300 is 'poor'; 301 to 400 is 'very poor', and 401 to 500 is 'severe'.

A report from the centre-run System of Air Quality and Weather Forecasting And Research held some hope for the national capital amid renewed reports of crop burning. "Surface winds are slow and variable, and the wind direction at the surface and transport height is south-southwesterly, which is not quite favourable for efficient transport of fire plumes towards Delhi. In this condition, drastic deterioration of air quality is not expected over the next two days," the report said, predicting that the city's AQI will fluctuate between the higher end of "poor" category and the lower end of the "very poor" category.

The India Metereological Department, for its part, said that the city's air quality is likely to improve due to changing weather conditions. "A fresh western disturbance may impact the Western Himalayan region from October 18. It may also enhance the wind speed, which will help disperse pollutants," said Kuldeep Srivastava, a senior scientist with the department.

Meanwhile, the authorities banned generator sets -- barring those used for essential and emergency services -- across the national capital region in an attempt to halt the rise in pollution. It was part of the Graded Response Action Plan, a set of strict anti-pollution measures to be taken in keeping with the severity of the pollution.

(With inputs from PTI)