WASHINGTON (Reuters) - The U.S. Nuclear Regulatory Commission (NRC) on Tuesday unveiled a letter showing that 17 of the country’s nuclear reactors have parts from Areva SA’s Le Creusot forge in France, which is under investigation for allegedly falsifying documents on the quality of its parts.

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The number of reactors was more than the nine the NRC had previously disclosed.

Last month authorities in France opened an investigation into decades of alleged forgery of documents relating to the quality of parts produced at Le Creusot and used in power plants around the world.

Areva, a nuclear and renewable energy firm, furnished the information to the U.S. regulator last month but had urged the agency to keep it private, saying it was material to the business of nuclear power generators. The NRC told Areva it did not consider the information to be so and released it 10 days after receiving it.

The parts at reactors include a reactor head at Xcel Energy Inc’s Prairie Island reactor in Minnesota, reactor vessel heads at two of Dominion Resources Inc’s reactors at the North Anna plant in Virginia, and another vessel head at Dominion’s reactor in Surry, Virginia. Some of the components were made by other companies but include parts from the Le Creusot.

“We have four components with forgings from Le Creusot and have verified that all are fine. They all check out and meet our design criteria and there are no problems,” said Richard Zuercher, nuclear spokesman at Dominion Resources Inc.

Xcel Energy Inc said previously that some components of the two reactor vessels were made at Le Creusot in the early 1970s. “Our testing and inspections are rigorous and have not identified any issues,” Colleen Mahoney, an Xcel spokeswoman said last week.

Anti-nuclear power groups such as Greenpeace had urged the NRC to release the information. The NRC has maintained that the parts and the reactors were completely safe. Areva told the NRC that a review of paperwork anomalies “has not found any safety concerns.”

French nuclear regulator ASN said Areva told it of evidence of irregularities in about 400 components produced at Le Creusot since 1965.

David Lochbaum, an expert on nuclear energy at the Union of Concerned scientists, said the Le Creusot issue was “troubling from both trust and public safety perspectives” because to a large degree both the NRC and U.S. nuclear power plants depended on vendors to certify their work.