Nearly 270 enterprises were found to have violated environmental regulations when three waves of heavy air pollution hit large parts of the northern and northwestern China in November, the Ministry of Ecology and Environment said on Tuesday.

Emergency measures to cut emissions, such as halting construction and increasing road sprinklers, are taken when alerts for heavy pollution are issued, according to the ministry.

It said Hebei province saw 166 companies failing to comply with the emission guidelines in November, accounting for 62.2 percent of the total 267 enterprises and institutions.

The ministry also identified 54 violators in Henan province, 20 in Shanxi province, 20 in Shandong province, four in Shaanxi province, two in Tianjin and one in Beijing.

More than half of these violations occurred because industrial enterprises failed to prevent and control their pollutants.

Others issues include wind-borne dust, open burning and the use of coal-fired boilers, the ministry said.

Local authorities have been notified of environmental issues in their regions and ordered to start investigating and handling of violators.