WASHINGTON — The Defense Department’s internal watchdog is investigating a $400 million border wall contract awarded to a firm that used multiple appearances on Fox News to push for the job.

The Pentagon’s inspector general sent a letter Thursday to House Homeland Committee Chairman Bennie Thompson telling him the contract awarded to North Dakota-based firm Fisher Sand and Gravel Co. would be audited. Thompson, D-Miss., asked for the review last week, in part over concerns the proposals did not meet operational requirements and prototypes came in late and over budget.

Tommy Fisher, the head of the family business, said Thursday there would be “nothing to find” in an audit.

“We were told we were the lowest price and the best value,” he said. “We look forward to working with the Army Corps of Engineers.”

The border wall is one of Trump’s top priorities. He campaigned on a promise to build a “big beautiful wall” between the U.S. and Mexico,” said Mexico would pay for it, and promised to build 450 to 500 miles by the end of 2020. Mexico is not paying for the wall and, as of Nov. 1, Trump had built 78 miles.

Trump’s effort to push through funding, using money  from the Pentagon  after Congress refused to fund the wall has been met with resistance and lawsuits. A federal judge this week blocked the administration from spending some Defense Department money on the the barrier — the money includes the contract for Fisher.

The company was awarded a contract Dec. 2 to build 31 miles of wall in Arizona, part of a series of contracts to push out increased mileage. Fisher had made a number of appearances on Trump’s favorite cable news channel — Fox News — talking about his desire to win a contract. His firm, though, has little experience with such construction and a previous proposal was rejected.

Fisher said his company could do the work for $13 million a mile. He said the next closest bid was $20 million a mile.

A letter from the Army Corps when Fisher was awarded the contract said the company’s proposal was both technically acceptable, and the best priced.

Two administration officials familiar with the matter told The Associated Press this year that Trump aggressively pushed the Fisher firm’s bid with the heads of Homeland Security and the Army Corps of Engineers, which manages wall contracts. The interference in federal contracting by a president concerned some overseeing the process but, the officials said, Trump insisted Fisher could get the wall up faster and cheaper than other bidders. The officials weren’t authorized to speak about internal discussions and spoke to the AP on condition of anonymity.

Thompson had said one of his concerns was that officials from Homeland Security, the department managing border security, had toured a private barrier built by the company shortly before the contract was awarded.

The Pentagon watchdog said it was assessing how to complete the audit and would formally announce it soon.

Thompson said he was pleased.

“The company had never been awarded a construction contract before and their wall prototype was late and over budget,” he said in a statement. “Given the President’s multiple endorsements of this company and the amount of taxpayer money at stake, I remain concerned about the possibility of inappropriate influence on the Army Corps’ contracting decision.”

The award was the second-largest contract in the company’s history. Previously, Fisher built highways, sold heavy equipment and did excavation work. The company unsuccessfully sued the government in April when it was not awarded a similar contract.