A measure calling for an in-depth audit of the Southwest light-rail line, a project riddled with cost overruns and delays, won approval Thursday in the Minnesota House.

The bill drew widespread bipartisan support and was passed 129-1.

It calls on the Legislative Auditor's office to conduct a special review of the state's most expensive public works project and sets aside $200,000 to pay for it. The Senate Finance Committee passed a companion bill Thursday.

The Metropolitan Council recently announced that the project would cost an additional $450 million to $550 million, bringing the total cost to between $2.65 billion and $2.75 billion.

The 14.5-mile line is about 60% complete and will link downtown Minneapolis to Eden Prairie by way of St. Louis Park, Hopkins and Minnetonka. Passenger service is expected to begin in 2027, about four years later than earlier planned.

"I think the situation is unprecedented; it's a very urgent matter," said Rep. Frank Hornstein, DFL-Minneapolis, one of the bill's sponsors.

Last summer, Hornstein and Sen. Scott Dibble, DFL-Minneapolis, asked the legislative auditor to review the project after a $200 million Hennepin County contingency fund was tapped to cover unexpected costs.

The legislative auditor released a memorandum in October that highlighted a "prolonged and significant" difference of opinion on construction issues between the Met Council and a major contractor.

The memo contained "enough alarms and red flags we felt we had do something out of the ordinary" and request a more involved review, Hornstein said Thursday. Gov. Tim Walz said in February that he supported the audit.

The review includes a laundry list of items to be scrutinized, including project costs, cost overruns, scope changes, delays, the qualifications of project staffers, construction quality and management. It could take up to a year to complete..

Southwest's construction is primarily being funded by a $929 million federal grant. Hennepin County is paying a large portion of the rest, mostly through atransportation sales tax. The state contributed $30 million to the project and is not on the hook for operating and maintenance costs once service begins.

Several House Republicans unsuccessfully proposed changes to the bill that could have paused or killed the project.

"This is the biggest waste of money I've ever seen in my lifetime," said Rep. Kurt Daudt, R-Crown. "Let's just kill it and be done with it."

Lawmakers approved an amendment calling for the Met Council to immediately alert lawmakers if the project goes 5% over budget or if passenger service is delayed by six months or more.

They also passed an amendment requiring the council to update the Legislature on Southwest's timeline and budget twice a year.

In a statement, the Met Council said it supports the audit and "is always open to and welcomes discussions on ways to improve the long-term vitality of our region. The work of [Southwest] is too critical to not have a transparent dialogue addressing the complexities of this project."