BEIJING - Shares in firms engaging in business related to environmental protection boosted Chinese stocks on Tuesday morning after hazardous air pollution shrouded parts of the country for several straight days.

The benchmark Shanghai Composite Index gained 0.42 percent to end the morning session at 2,321.55. The Shenzhen Component Index went up 0.29 percent to close at 9343.11.

The sub-index for the environmental sector led the rally by rising 5.24 percent during the morning session.

Some companies like Kelin Environmental Protection Equipment, Inc. and Zhejiang Feida Environmental Science & Technology Co Ltd saw their shares surge by the daily limit of 10 percent.

Beijing SPC Environment Protection Tech Co Ltd, a pollution treatment company, climbed 7.42 percent to 19.1 yuan.

Heavy fog has enveloped much of eastern and central China in recent days, causing highway closures and flight delays in several provinces.

Beijing's air has been heavily polluted. Readings for PM2.5, airborne particles with a diameter of 2.5 microns or less -- small enough to deeply penetrate the lungs -- were as high as 993 micrograms per cubic meter of air on Saturday evening.

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