BEIJING -- After government probes, seven more container shipping lines have offered to cut terminal handling charges in China, saving traders millions of dollars, authorities said Monday.

Shipping firms, including the Hong Kong-based Orient Overseas Container Line and Israel's ZIM Integrated Shipping Services, have written to the National Development and Reform Commission and the Ministry of Transport, promising to lower the charges, the commission said in a statement.

The reductions in the firms' average terminal handling charges ranged between 76 yuan ($11.1) and 127 yuan per TEU (20-foot equivalent unit), according to the commission, the country's top economic planner.

After the cuts, the firms will charge 633-731 yuan per TEU.

The commission said authorities had investigated the collection of surcharges by shipping lines since last year, following trading companies reporting the practice. Terminal handling charges are a major form of such surcharges.

Earlier this month, the commission said 11 container shipping lines had pledged to cut average terminal handling charges by 13-22 percent. They included the state-owned China COSCO Shipping and global giants Maersk Line and the Mediterranean Shipping Company.

"With their moves, the 18 shipping lines can reduce the burden on importers and exporters by a total of 4.6 billion yuan each year," the commission said.