BEIJING — Inspectors sent by China's Ministry of Environmental Protection have found environmental violations by imported waste processing firms, the ministry said Sunday.

As of Thursday, irregularities were found in 590 companies nationwide, or 66 percent of the total firms inspected.

On Thursday alone, out of 90 firms inspected, 51 firms were suspected of various breaches, including production without approval, lack of business records and failing to implement routine environmental monitoring.

The inspectors have advised local authorities on punishments on the firms.

The ministry launched a month-long campaign against pollution by a number of small companies processing imported waste at the beginning of July, sending 420 inspectors in 60 teams to localities.

Inspectors will focus on whether enterprises have passed environmental evaluations, violated rules of pollutant discharge, or illegally transferred waste imports, among others.

Local officials will be summoned for talks if they act slowly in dealing with problems, according to the ministry.

China is stepping up its fight against pollution and environmental degradation caused by decades of fast growth.

A reform plan to improve management of solid waste imports was adopted in April.