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After four Minnesota Vikings seasons at U.S. Bank Stadium, construction and design costs remain unresolved, the stadium’s public operator reported Thursday.

But officials were not yet ready to say what the specific issues were.

The Minnesota Sports Facilities Authority (MSFA), which oversees stadium operations, met in a closed-door session after its monthly public meeting to discuss attorney-client matters, then released a statement acknowledging ongoing mediation over a building issue but few clues about the scope or dollars involved.

The statement said the MSFA is in “confidential discussions” with “multiple parties involved in the design and construction of U.S. Bank Stadium.” It attempted to quell concerns about taxpayer liability, saying the MSFA would “fulfill its responsibility to safeguard the public’s investment in U.S. Bank Stadium.”

The MSFA statement also said discussions have been “collaborative” and “positive” and that a resolution is possible in the coming weeks.

If a resolution is reached, the MSFA board would have to publicly vote on it and release the details.

M.A. Mortenson, the general contractor, issued a written statement acknowledging the “discussions regarding construction closeout and matters involving Mortenson and other companies.”

The Vikings also issued a statement saying they’re participating with the MSFA and “support their efforts to protect both the public investment and this community asset.”

The $1.1 billion publicly subsidized stadium opened in August 2016 on the site of the former Metrodome, with taxpayers covering nearly $500 million of the cost.

While the project was completed after just 18 months of construction, there were issues along the way, notably with moisture and the black zinc panels that form the exterior skin of the building. MSFA Chairman Michael Vekich wouldn’t say whether previously identified issues with the building were the focus of mediation.

The rectangular zinc panels initially were fastened to the building along their lower edge. But before the facility opened, some of them flapped loose in a summer storm.

When the panels continued to come loose in certain winds, a subcontractor spent months assessing the problem and reinforcing the panels’ connection to the building.

In the summer of 2017, Mortenson said it had found additional moisture concerns. The plan was to replace moisture barriers on the joints of the building’s interior panels and add a new layer of Tyvek under the zinc panels.

The work affected fewer than 10% of the building’s metal panels, a Mortenson executive said at the time. But the cost of the repairs has never been publicly explained, nor has anyone ever said whether the flaws were in the stadium’s design, materials or construction.

More than two years ago, a Mortenson executive said the MSFA would pay for the additional Tyvek.

He later said the taxpayers should not pay for it.

The MSFA is the publicly funded body that operates the stadium on behalf of taxpayers, and the Vikings are the building’s main tenant.