Pollution levels have soared in the Indian capital and surrounding northern regions of the country, a day after thousands of people defied a ban on firecrackers to mark Diwali, the Hindu festival of lights.
New Delhi residents woke to thick smog on Sunday as firecracker emissions added to already high levels of pollution brought on by crop stubble burning in the region.
Air quality index levels at most monitoring stations in and around the city were in the severe category, with PM2.5 levels hovering around the 500 mark.
That is more than 20 times the limit deemed safe by the World Health Organization and is roughly the equivalent of smoking 25 cigarettes a day in terms of the damage to people's health.
Scattered rain on Sunday evening slightly brought down PM2.5 levels in some areas but pollution stayed a major topic of debate on social media.
While some residents complained of people not following the ban, others said it was unfair to blame firecrackers which are a traditional part of celebrations on the Hindu festival of Diwali.
Delhi, with 25 million inhabitants, has been ranked among the world's most polluted cities in recent years.
The air quality worsens in October and November when unfavourable climatic factors like low wind speed and seasonal crop stubble burning by farmers add to pollution from vehicles and industry.
The National Green Tribunal imposed a ban on the sale and use of firecrackers in Delhi until November 30, with punishment for violators ranging between 18 months and six years in jail.
But many residents defied the ban and firecrackers could be heard going off into the early hours of Sunday.
At least 55 people had been arrested by Saturday for selling firecrackers and 21 others for using them, Delhi Police said on Twitter.
Doctors have said the rising pollution may adversely impact people suffering from respiratory ailments related to COVID-19.
Delhi chief minister Arvind Kejriwal has said he sees pollution as the biggest reason behind the latest coronavirus spike in the city.
Delhi has been reporting more than 7,000 new cases daily over the past week.
Hospitals reported a shortage of intensive care beds for patients.
Federal Home Minister Amit Shah held a meeting with Kejriwal and other senior officials on Sunday to assess measures needed to tackle the latest spike.