Around 20 million people in India’s capital woke up on Wednesday breathing the most polluted air of any major city in the world, a day after celebrations for the Diwali festival, during which revelers typically set off fireworks and firecrackers.

At least eight people were killed on Monday in a car explosion near the historic Red Fort in a densely populated area of the Indian capital of New Delhi, a police spokesperson said. It was a rare blast in the heavily guarded city of more than 30 million people.

India's capital Delhi is blanketed in toxic smog every autumn, but the pollution is already so bad that it's drawn protests as authorities tell students to stay home.

At least eight people were killed in a car explosion on Monday near the historic Red Fort in a densely populated district of the Indian capital Delhi, a city police spokesperson said, though the exact cause of the blast is still being investigated.

India’s top security official said the cause of the blast, near the Red Fort in the capital, was still being investigated.

Dr Umar is the key accused who carried out a suicide blast near Red Fort in Delhi on November 10, leaving 13 people dead and several injured.

CCTV footage from Delhi captures the exact moment a car exploded, sending shockwaves through the area. Authorities have cordoned off the site and launched an investigation to determine the cause of the blast.

Those responsible for the explosion “will not be spared,” Prime Minister Narendra Modi of India said. The blast killed at least eight people near a subway station at evening rush hour.