India, Nov. 3 -- Delhi's annual pollution crisis appears to have arrived earlier than usual, with air quality deteriorating sharply to the 'very poor' category days before Diwali.

While crop-residue burning in Punjab and Haryana remains a major concern, an unusually high number of agricultural fires across Pakistan's Punjab province may also be adding to the regional pollution burden.

Delhi's air quality index (AQI) entered the 'very poor' category for the first time this season on Monday, November 2.

By Tuesday, the average AQI stood at around 330, while at least three monitoring stations recorded readings above 400, placing them in the 'severe' category.

The early deterioration has raised concerns about another prolonged spell of wi...