MONTPELIER, Vt. – Owners of the Vermont Yankee nuclear power plant say their representatives never intentionally misled the state about the presence of underground piping that can carry radioactive material underneath the plant in Vernon.

In a 114-page report filed Thursday, Entergy Corp. said its agents and representatives gave incomplete answers to questions by the state Public Service Board and should have corrected them later, but that they never tried to deceive.

It blames the misstatements, in part, on differing interpretations of “underground piping.”

But Vermont’s top regulator, Public Service Commissioner David O’Brien, criticized Entergy’s internal investigation and report, saying no one from the state was interviewed.

“It’s a one-sided investigation. It’s 180 degrees, not 360 degrees, in the sense that the only people interviewed were Entergy employees,” said O’Brien, who was still reviewing it Friday.

State officials and a contractor working for the state at Vermont Yankee were told in 2008 and 2009 that the plant didn’t have the kind of underground piping that could carry tritium or other radioactive substances.

But the plant does. In January, plant officials announced that tritium had been found in a groundwater monitoring well at the plant. Five days later, it was revealed that plant officials had falsely said such pipes didn’t exist at Vermont Yankee.

The revelation, which came as the state weighed Entergy’s bid for a 20-year extension of the nuclear plant’s operating license, drew irate reactions from state officials and environmental advocates and a stern rebuke by Gov. Jim Douglas, a Vermont Yankee supporter.

The report filed Thursday on behalf of New Orleans-based Entergy Corp. gave the results of a probe by hired law firm Morgan Lewis of Washington, D.C.

The firm reviewed more than 65,000 documents and interviewed 29 people, according to the report.

It said that in May 2009 testimony before the Public Service Board, Entergy Nuclear Vice President Jay Thayer didn’t mean to give misleading information, and that others in the company identified the discrepancies but failed to correct or clarify them.

Still, the company’s investigator “did not find that any (Entergy) personnel or representatives intentionally misled third parties about the existence of underground piping at VY that carries radionuclides,” the report said.

Arnie Gundersen, a former nuclear industry executive who now works as a consultant to Vermont lawmakers on Vermont Yankee issues, dismissed the report’s conclusion.

He said Vermont Yankee officials knew as early as August 2009 that misrepresentations had been made about the piping issue, but that no attempt was made to correct them.

Of the report, he said: “They cherry-picked the data to support the conclusion they needed to reach. They went in knowing the answer. The report selectively chooses snippets and ignores anything on the record that disagrees with it.”