BEIJING (BLOOMBERG) - China will jail forty-seven steel company officials for faking air pollution data, in a sign that Beijing's crackdown on firms that are flouting environmental rules is intensifying.

The officials who worked at four mills in Tangshan city near Beijing, China's top steel-making hub, were given prison sentences from six to eighteen months, the municipal government said in a statement on its WeChat channel that cited court documents.

The sentences underscore Beijing's push to clean up a major source of air pollution. Authorities have ramped up environmental controls on the steel industry over the past decade in a bid to reduce bouts of dirty air.

The goal is to have more than 530 million tons of capacity in the "ultra-low emissions" category by 2025.

The officials - at Tangshan Great Wall Steel Group, Songting Iron & Steel Co, Hebei Xinda Iron & Steel Group Co, Tangshan Medium Thick Plate Co and Tangshan Jinma Steel Group - interfered with monitoring devices to allow the release of large quantities of pollutants in March 2021, according to the statement.

Two of the companies - Tangshan Songting and Hebei Xinda - were also fined 4 million yuan to 7 million yuan (S$851,500 to S$1.49 million).

It's part of a long-running environmental crackdown in the steelmaking hub.

Tangshan Jinma and another three mills were found guilty last March of not complying with production cuts put in place to reduce pollution.