BEIJING - Beijing collected over 100 million yuan ($15.8 million) in fines from polluters in the first nine months of the year, almost double the sum in the same period of 2014, the city's environmental bureau said on Tuesday.

From the start of January to the end of September, it lunched investigation into 2,492 cases, mostly concerning air and water pollution and construction projects failing to meet standards.

The bureau said it has stepped up law enforcement since the beginning of this year. About 11,620 companies and organizations were checked.

The fines have grown after a harsher environmental protection law came into effect on Jan 1. It allows fines to accumulate on a daily basis for enterprises that fail to rectify violations, closing the loophole of cheap one-off penalties.

The bureau will continue to target coal burning, open burning of wastes and dust from construction site to curb smog as winter approaches, it said.

The fines are likely to continue growing following the October introduction of fees for emitters of volatile organic compounds (VOCs), which can form the tiny, hazardous airborne particles known as PM2.5 following chemical reactions in the atmosphere.

Packagers, printers and manufacturers of furniture, petrochemicals, automobiles and electronics will be subject to the charge, which will range from 10 yuan to 40 yuan per kg of matter they discharge.

The fees are higher than the cost for enterprises to properly treat their emissions, so it should encourage them to adopt cleaner practices.

Smog has become a major environmental issue in Beijing. The central government has ordered the city to cut PM2.5 from 2012 levels by 25 percent by 2017.