MINNEAPOLIS (AP) — An investigation by Minnesota utility regulators blames Xcel Energy Inc. for major cost overruns during a project to upgrade its nuclear plant in Monticello.

Xcel disagrees that it’s to blame.

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Reports say experts hired by Minnesota utility regulators found Xcel managers didn’t fully plan for the job and didn’t have adequate oversight. The investigation also found Xcel misleadingly blamed the U.S. Nuclear Regulatory Commission for some costly delays.

The project rose from an estimated $320 million in 2008 to $665 million when it was completed last year. The final cost could reach $748 million.

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The utility is asking regulators to have ratepayers pay for the cost of the upgrade.

Xcel will file a reply to issues raised in the investigation next month.

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