A thick haze caused by plumes of toxic smoke enveloped Delhi and its surrounding areas on Sunday. According to government-run monitoring agency System of Air Quality and Weather Forecasting and Research, or SAFAR, the air quality index in the national Capital was 625 and in the “severe” category at 12 pm.

SAFAR measures Delhi’s air quality based on index values recorded at up to nine stations spread across the city and one each in Noida and Gurugram. Ten of these stations recorded air quality in the “severe plus emergency” category on Sunday. Gurugram was the most polluted with an AQI of 737.

An AQI between 0-50 is considered “good”, 51-100 “satisfactory”, 101-200 “moderate”, 201-300 “poor”, 301-400 “very poor” and 401-500 “severe”. An index above 500 falls in the “severe-plus emergency” category. Anything above 400 poses a risk for people with respiratory illnesses and can also affect even those with healthy lungs.

Authorities on Friday had declared a public health emergency and closed schools and all construction activity until next week as pollution in the city hit its worst level this year.

Also read: Centre, Arvind Kejriwal continue blame game as Delhi smog thickens on Sunday

Here are pictures of the pollution:

Tourists cross a road to visit the India Gate under heavy smog conditions in Delhi on November 3. Image credit: Sajjad Hussain/AFP
Hindu devotees worship the Sun god in the river Yamuna during the Hindu religious festival of Chathh Puja in New Delhi, India, November 3, 2019. Image credit: Reuters/Adnan Abidi
Stubble burning at a field near Patiala on November 2, 2019. Stubble burning has also caused the air quality to deteriorate. Image credit: PTI
A crow sits on a barricade in front of India Gate amidst smog in New Delhi on November 3. Image credit: Reuters/Adnan Abidi
Hindu women worship the Sun god in the polluted waters of the river Yamuna during the Hindu religious festival of Chhath Puja in New Delhi November 3, 2019. Image credit: Reuters/Adnan Abidi
Devotees leave after Chatth Puja on a smoggy morning in New Delhi on November 3. Image credit: Reuters/Adnan Abidi
Motorists drive along a road under heavy smog conditions, in New Delhi on November 3, 2019. Image credit: AFP/Sajjad Hussain
A view of a traffic jam due at Jamuna Bazaar Ring road in New Delhi on Saturday, November 2, 2019. Image credit: PTI
Bangladesh's cricketers wearing face masks attend a practice session under heavy smog conditions at Arun Jaitley Cricket Stadium in New Delhi on November 2, 2019. The first T20 international cricket match of a three-match series between Bangladesh and India starts on Sunday. Image credit: AFP

#DelhiAirEmergency was trending on Twitter as many users put up photos of the toxic smog in and around the Capital.

Some Twitter users pointed out the irony of the prime minister saying in Thailand today that it was “the best time to be in India”.