Air pollution chokes New Delhi every winter, but this year's smog has already derailed everything from transport and road work to schools.

Authorities in India’s capital have shut schools, halted construction and banned non-essential trucks from entering the city after air pollution shot up to its worst level this season.

Around 38% of the pollution in New Delhi this year has been caused by stubble burning - a practice where stubble left after harvesting rice is burnt to clear fields - in the neighbouring states of Punjab and Haryana, according to SAFAR, a weather forecasting agency under the ministry of earth sciences.

By Tanvi Mehta NEW DELHI (Reuters) -Toxic smog engulfed much of northern India on Monday and pollution readings in New Delhi hit their highest of this pre-winter season, after dense fog overnight. Visibility dropped to 100 metres in the capital and at least eleven flights were diverted.