A haze of smoke continued to blanket New Delhi and the National Capital Region on Wednesday as pollution levels deteriorated to the “severe” category. The haze can be “purely” attributed to stubble burning in nearby states, whose share in Delhi’s pollution rose to the season’s highest of 35% on Wednesday, said the Centre-run System of Air Quality and Weather Forecasting and Research, or SAFAR.

The agency said that extremely calm surface wind conditions in Delhi on Tuesday night “further aggravated the situation by accumulation of pollutants”. However, it said that effective stubble fire counts of Haryana and Punjab had now significantly declined to 1,057 during the past day as compared to 2,577 on the previous day.

According to the Central Pollution Control Board, the 24-hour average air quality index remained over 410 the entire day and deteriorated to 419 by 4 pm. Air this bad “affects healthy people and seriously impacts those with existing diseases”, according to the agency. The Air Quality Index takes into account five chief pollutants – particulate matter with a diameter less than 10 micrometres (PM10), PM2.5, ozone, nitrogen dioxide, and carbon monoxide.

The air quality in the city was in the “very poor” category on Tuesday, with a reading of 400 at 4 pm.

Pollution levels have increased so much since Diwali celebrations that the Indian men’s cricket team could make outdoor training sessions optional ahead of Sunday’s first Twenty20 International against Bangladesh in New Delhi, a report said.

The Delhi government on Tuesday claimed that farm fires in Punjab and Haryana had increased drastically since Monday, and the share of stubble burning in Delhi’s air pollution might peak, PTI reported.

SAFAR predicted a marginal improvement in the air quality on Thursday due to an expected increase in wind speed that will help disperse pollutants faster.

As the quality of air plummeted, Chief Minister Arvind Kejriwal on Tuesday appealed to Punjab and Haryana “with folded hands” to take concrete steps against stubble burning so that the national capital does not become a “gas chamber”.

“At our level, we are making all possible efforts and will continue to do so,” he tweeted.