Schools in India’s capital were shut on Thursday after a thick gray haze of noxious air enveloped the city for the third consecutive day, and angry residents blamed authorities for allowing an annual children’s run.

Buildings and monuments were largely obscured by smog and an official health advisory asked people to avoid all physical activity outdoors.

The air quality index exceeded 460, nine times the level recommended by the WHO, according to the state-run Central Pollution Control Board. In some places, the index crossed the 500 level.

Still, hundreds of children took part on Thursday in the annual “Run for Children” race organised by a nonprofit group called Prayas.

Residents took to social media and blamed authorities for allowing the run after pictures surfaced of children without protective masks.

The event was organised to mark the birthday of India’s first prime minister, Jawaharlal Nehru, which is celebrated as Children’s Day in India.

“It was a symbolic event and children didn’t run beyond 200 meters,” organizer Amod K. Kanth told The Associated Press.

Caught in the middle of the controversy, Kanth said the organisation had permission from the authorities and he was not directed to cancel the event.

New Delhi is one of the world’s most polluted cities, and winters have become a time of annual health woes when the city is covered in a toxic haze that obscures the sky and blocks sunlight.

Doctors in the city of 20 million people say many of their patients are complaining of ailments related to the filthy air they breathe.

Air pollution in northern India, including New Delhi, peaks due to smoke from agricultural fires in neighboring Haryana and Punjab states, which mixes with the city’s vehicle emissions and construction dust.

Authorities have resorted to emergency measures such as banning construction, cutting down traffic and prohibiting the use of diesel generators. But these steps have had little effect as state governments have failed to cooperate in tackling pollution.

Prime Minister Narendra Modi has not spoken about the crisis even though he frequently promotes government programs on Twitter and other public platforms.

With the pollution levels in New Delhi plunging, Chief Minister Arvind Kejriwal on Wednesday said that the temporary restrictions on private vehicles meant to reduce emissions could be extended if necessary.

Meanwhile, pollution is likely to decrease from Thursday night when wind speed picks up, according to the India Meteorological Department.

WHO data released last year showed India had 10 of the world’s 20 most polluted cities.