COLUMBIA, S.C. - Lawmakers have asked for an audit of the state Transportation Department, including a detailed explanation on how the agency has spent its money over the past three years.

The call for the audit came Wednesday, the same day agency staffers told transportation commissioners that some of the state's major road projects financed by the State Infrastructure Bank could run more than $96 million in the red, possibly forcing the department to cut back on new projects or road maintenance.

The letter requesting the audit asks for a detailed explanation of agency expenses for the past three fiscal years, the amounts spent on primary and secondary roads and a review of the agency's methods for measuring the results of its expenditures.

The lawmaker who asked for the Legislative Audit Council to examine the agency said the request doesn't mean he thinks the Transportation Department is doing a poor job.

"I feel like they do a good job and I want an independent entity to come in a take a look at it and either confirm that for us or tell us there is a problem," said Rep. Bobby Harrell, chairman of the House Ways and Means Committee.

Harrell said he asked for the audit after his father, transportation commissioner Bob Harrell Sr., requested it. Eight other members of the younger Harrell's committee also signed the request.

Other transportation commissioners have said in recent weeks that they would support a review of the agency.

The most outspoken has been Chairman Tee Hooper, who asked Elizabeth Mabry, executive director of the department, to step down, accusing her of running an agency with financial problems and poor morale. The other commissioners recently cast a 6-0 vote in support of her.

The audit has support from the executive branch too. "The governor has always been about looking under the hood of any state agency," said Will Folks, spokesman for Gov. Mark Sanford.

The five-member board made of citizens elected by the Legislature will decide whether to approve the audit next Wednesday.

The audit request came the same day Transportation Department officials reported a nearly $100 million shortfall in State Infrastructure Bank projects. The bank won't pay for any cost overruns, officials said.

About $66 million of the shortfall comes from the new Cooper River Bridge being built in Charleston. While officials said the project is essentially on budget, funding by the Infrastructure Bank didn't include demolishing the old bridges.

Other cost overruns stem from projects in Horry, Lexington and Beaufort counties and include condemnation challenges in court and contractor's claims, officials said.

Mabry said the $96 million overrun isn't that big compared to the $3 billion of projects financed by the Infrastructure Bank.

But unless they can raise new revenue, commissioners will have to cut road projects or maintenance to pay for the extra $96 million, said Keith Bishop, deputy director for finance and operations.

Two other possibilities could be choosing to borrow the money through bonds or attempt a more creative financing through the Infrastructure Bank.

Hooper said he doesn't want to add to the agency's current debt, estimated between $600 million and $700 million.

Commissioner John Hardee said one option is off the table for him.

"I will not cut maintenance," he said. "There are a lot of roads out there that are deteriorating."