PORTLAND – Federal prosecutors filed suit Monday against Maine utility regulators and Verizon to block disclosure of confidential information linked to questions of whether the company broke the law by cooperating with a domestic surveillance program.

The U.S. District Court complaint came after an Aug. 9 order by the Public Utilities Commission that Verizon attest in a sworn statement to its previous public comments about the National Security Agency’s warrantless eavesdropping program.

The suit said compliance with the order would “place Verizon in a position of having to confirm or deny the existence of information that cannot be confirmed or denied without causing exceptionally grave harm to national security.” In a letter last month, the U.S. Department of Justice served notice to the PUC that it was prepared to go to court if the agency elected to move ahead with an investigation into alleged privacy law violations.

The commission stopped short of ordering the investigation. Instead, it gave Verizon two weeks to provide additional information. The company said in a May news release that it would not discuss any relationship with the NSA program but denied media reports that it had provided customer call data or records.

Similar cases have surfaced in other states in response to news reports alleging that phone companies have cooperated with government surveillance efforts. The Justice Department has filed lawsuits to prevent disclosure of confidential information in New Jersey and Missouri.

Named as defendants in the Maine lawsuit were Kurt Adams, the PUC chairman; Sharon Reishus, a commissioner; Dennis Keschl, the commission’s acting administrative director; and Verizon New England.

Messages left for Phil Lindley, a commission spokesman, were not immediately returned.

The lawsuit argued that the PUC lacked authority to issue its order to Verizon because of the federal government’s exclusive control over national security and foreign intelligence-gathering activities.

A group of 22 Mainers filed a complaint in May asking the PUC to order Verizon to answer whether it provided telephone records and information to the federal government without customers’ knowledge or consent.