Pakistan’s second city, Lahore, will close primary schools for a week due to record pollution, government officials said on Sunday, to avoid exposing millions of children to smog several times higher than levels considered dangerous.

For days, the city of 14 million has been engulfed by smog, a mix of smog and pollutants caused by low-quality diesel fumes, smoke from seasonal agricultural burning and winter chills.

The air quality index, which measures a series of pollutants, exceeded 1,000 on Saturday – well above the level of 300 considered “dangerous” – according to IQAir data. The Punjab government also recorded spikes of over 1,000 on Sunday, which it called “unprecedented”.

“The weather forecast for the next six days shows that wind patterns will remain the same. Therefore, we will close all public and private primary schools in Lahore for a week,” said Jahangir Anwar, a senior environmental protection official in Lahore.

“All classes” for children up to 10 years old, “public, private and special education… will remain closed for one week” from Monday to Saturday, reads a local government decision.

The decision adds that the situation will be evaluated again next Saturday to determine whether to extend the school closure.