Pakistan's Punjab declared a health emergency due to toxic smog on Friday, banning construction, shutting schools for another week and moving universities online, with a three-day lockdown possible, the province's senior minister said on Friday.

With smog intensity escalating in Lahore at the end of October, affecting its 13 million residents, the Punjab government imposed a “green lockdown” and set up a “smog war room.”

The government of Pakistan’s most polluted province has launched a new policy to address a protracted smog crisis, after the world’s worst air shuttered schools and saw 900 people seek hospital treatment in a single day.