Residents in India's northern states woke up to another day of poor air quality on Tuesday, as a layer of dense fog shrouded most of the region, and pollution in the capital Delhi remained severe.

Toxic smog engulfed much of northern India on Monday and pollution readings in New Delhi hit their highest of this pre-winter season.

Residents of Delhi woke up to a thick blanket of toxic smog, prompting the city to cancel in-person classes, halt construction and limit traffic, as the Indian capital city's air-pollution levels surged past 60 times the World Health Organization's recommended daily maximum.