Visibility fell sharply in Delhi this week as a toxic mixture of smoke and fog shrouded the Indian capital even before winter sets in. Here is a look at the problem, and what triggered it. HOW BAD WAS THE SMOG?

Thick smog shrouded New Delhi and other cities around South and Southeast Asia as air pollution levels soared Thursday.

Air pollution choking New Delhi has ground outdoor work to a halt and disrupted air travel in the Indian capital.

A toxic haze enveloped India's national capital on Wednesday morning as temperatures dropped and pollution surged, reducing visibility in some parts and prompting a warning from airport authorities that flights may be affected.