India's federal pollution regulator has warned coal-fired power plants around New Delhi that they could be shut down for failing to comply with deadlines to meet emissions standards, according to sources and a letter reviewed by Reuters.

The move comes as New Delhi and other nearby cities in north India have been struggling with some of the worst air pollution levels on Earth, prompting local governments to shut schools and declare health emergencies this month.

The proposed action, if implemented, could be the strictest action yet on noncompliant utilities, which had already won an extension on a December 2017 deadline for power plants to meet emissions standards, after extensive lobbying by the industry.