BEIJING -- Several cities in North China were criticized Saturday for lazy environmental protection efforts in response to severe air pollution.

Inspection teams from the Ministry of Environmental Protection were sent to the provinces of Shanxi and Hebei earlier this month.

The city of Linfen in Shanxi did not issue a red alert when the city was shrouded in smog earlier this month, and only issued a yellow alert in the first place and an orange alert after being urged by the inspection team, the ministry said in a statement.

Six of 25 coal companies in Linfen did not complete emission management upgrading to meet environmental protection standards by the end of October, said the ministry.

Some industrial companies in the city of Tangshan in Hebei did not obey the government rules of production halt in a certain period of time, a move aiming at reducing pollution, noted the statement.

Smog was forecast to hit Hebei, Beijing and Tianjin over the next three days, the National Meteorological Center said Saturday.

China has a four-tier warning system for severe weather, with red being the most serious, followed by orange, yellow and blue.