Lahore has become the latest megacity to shut down as pollution chokes swathes of South Asia, where nearly 50 million people have been breathing toxic air for nearly a week.

Pakistan’s second-most populous city—with more than 13 million people—has shut down schools and closed public parks, malls and offices after the air quality index (AQI) this week spiked to more than 400, according to IQAir. That number is considered “hazardous” by the Swiss air tracking company.

Authorities in Pakistan’s Punjab province have imposed an “environmental and health emergency” in three cities—Gujranwala and Hafizabad in addition to Lahore—until the situation improves, its chief minister Mohsin Naqvi said this week. The three cities combined account for more than 15 million people.

The statement from Naqvi’s office indicated that there would be a limited movement of people to and from these areas by public and private transport. The government has also restricted the gathering of more than four people in one place.

The pollution spike in Pakistan comes after neighboring India saw smog blanket its capital, New Delhi, last week as colder temperatures trapped pollution particles, creating a toxic haze that reached hazardous levels.

Traditionally, toward the end of the year after the winter harvest, millions of farmers clear their leftover rice stubble by setting fields alight to prepare for the incoming wheat crop. This, together with vehicular and industrial pollution, has created copious amounts of smog across the areas.