Pakistan ’s smog situation has gone from bad to worse as air pollution rose to a record in Lahore. Sensors tracked by the Swiss monitor IQAir recorded an air quality index of 1,300 in the country’s second-largest city at 5 p.m. local time, the highest this year and well beyond a level of 50 that is deemed safe.

Record-high air pollution in Pakistan’s cultural capital of Lahore is sending more people to hospitals and private clinics and the city authorities warned a complete lockdown could be imminent if residents fail to don face masks and follow other guidance related to smog.

Pakistan's second city of Lahore will close primary schools for a week over record pollution, government authorities said Sunday, to avoid exposing millions of children to smog several times above levels deemed dangerous.

The air quality index is alarmingly high in Pakistan and India. This week, smog has drastically reduced visibility, obscuring views of landmarks such as the Taj Mahal in Agra. Consequently, many flights have been delayed.