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.

Authorities in India are investigating a deadly blast near a busy metro station in New Delhi. The explosion late Monday near the historic Red Fort killed at least eight people and injured several others.

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.

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.

A car blew up near the historic Red Fort in India's capital New Delhi, killing at least eight people, police said, adding that the cause remained unclear.

The move follows a weekend protest where police detained dozens of people demanding cleaner air, a rare public demonstration against pollution in the Indian capital.