BEIJING, Feb. 21 -- The Ministry of Environmental Protection on Friday blacklisted companies in the coastal city of Tianjin for breaking the air pollution rules.

The ministry made the report after secret investigation in suburban areas of Tianjin.

The ministry listed construction sites and companies that had failed to take anti-dust measures, especially in densely populated regions.

The ministry found it was common in Tianjin to burn grass and waste near communities and highways, and called for an end to such practices.

The ministry also reported companies with illegal emissions and listed their malpractices.

China is under pressure to meet emissions targets by 2015, deputy minister of environment protection said in February.

On Thursday, Beijing was on yellow alert for heavy air pollution over the next three days, with children and the elderly being advised to stay indoors.

Beijing, its neighbors Tianjin and Hebei provinces, as well as central and western Shandong Province can expect heavy air pollution for the next week, according to a joint weather forecast issued by the China Meteorological Administration and the Ministry of Environmental Protection.