Ministers in Pakistan’s Punjab province on Monday blamed Indian winds for worsening smog here, urging Indian authorities to take the matter seriously, after the air quality index in the capital reached a record level during the weekend.

Toxic gray smog has sickened tens of thousands of people, mainly children and the elderly, since last month, when air quality began to worsen in Lahore, the city bordering India. The concentration of PM 2.5, or tiny particles, in the air approached 450, considered dangerous, the Punjab Environmental Protection Department said.

“The direction of the wind brings air from India to Pakistan, but India does not seem to take this problem as seriously as it should,” Punjab Information Minister Azma Bokhari told the media. He urged the Indian part of the state of Punjab to take this matter seriously.

“Delhi today ranks first in smog levels, closely followed by Lahore in second place. Delhi’s air quality index is around 393, while Lahore’s is close to 280,” he said, adding that China has been fighting smog for the last 26 years.

Earlier, Punjab Chief Minister Marriyum Aurangzeb said the province was going to request Pakistan’s foreign ministry to take up the issue of cross-border pollution with India.

“Easterly winds from Amritsar and Chandigarh are pushing the air quality index in Lahore to over 1,000 for the last two days,” he said.

“The wind from India towards Lahore is driving smog to dangerous levels and the wind is likely to maintain its direction for at least the next week. People should take care of themselves by avoiding leaving their homes unnecessarily. The elderly and children should be especially careful,” Aurangzeb said.

Punjab Chief Minister Maryam Nawaz also called for climate diplomacy with India and said she would soon write to the chief minister of the Indian part of Punjab to jointly address the smog issue.

Meanwhile, the Punjab government closed primary schools in Lahore for a week in the wake of rising smog.

The government has already closed schools for children with special abilities for three months.

Lahore was once known as a city of gardens, which were omnipresent during the Mughal era from the 16th to the 19th century. However, rapid urbanization and increasing population growth have left little room for vegetation.