Some areas in northern China have been given permission to resume using coal or other available fuels to guarantee winter heating services for residents, according to a report on Thursday.

In a document released on Monday marked “extra urgent”, the Ministry of Environmental Protection said areas within or neighboring the Beijing-Tianjin-Hebei cluster could restart consuming coal “if their projects to replace coal-powered heating units with gas and electricity facilities were not finished”, news website The Paper reported.

The document, which was sent to 28 cities, including some in Henan, Shandong and Shanxi provinces, stressed that “the priority is to guarantee heating service for residents”.

Some places have been left without heat due to a failure to complete new clean-energy boilers in time for the start of winter, resulting in freezing homes and schools, media have reported.

Burning coal for central heating services has been a major contributor to the severe smog experienced in northern China in recent winters. Therefore, replacing coal-powered facilities with cleaner units is essential to easing air pollution, the ministry said.