The top Democrat on the Senate Armed Services Committee is requesting an investigation by the Government Accountability Office into recent decisions by the Army Corps of Engineers to award politically connected companies with contracts for border wall construction.

The request follows the awarding of a $400 million contract to Fisher Sand & Gravel, a company whose work has been touted by President Donald Trump, acting Homeland Security Secretary Chad Wolf and others close to Trump's orbit.

NBC News first reported that the Defense Department's inspector general was looking into the process that led to Fisher's win.

In his letter to the Government Accountability Office, or GAO, Sen. Jack Reed of Rhode Island asked the comptroller to investigate, among other questions, "to what extent, if any, did outside influence impact the contracting and selection criteria and award process?"

Reed also asked the comptroller to look into whether officials of the Defense Department and the Army Corps of Engineers had any contact "direct or indirect" with "any other administration officials and bidders related to border wall contract awards."

As seen from Tijuana, Mexico, a construction crew installs sections of the U.S.-Mexico border barrier to replace smaller fences on Jan. 11, 2019. Mario Tama / Getty Images file

A spokesperson for the GAO said the agency has received the request but has not made any decisions yet.

Fisher Sand & Gravel became entangled in controversy after The Washington Post reported that Sen. Kevin Cramer, R-N.D., held up the confirmation of a White House official in demanding to see border wall contracts that had gone out to other companies. Cramer had repeatedly pushed the White House to consider Fisher, a company from his home state.

Officials from the Department of Homeland Security told NBC News that Trump repeatedly pushed both publicly and privately for the Army Corps of Engineers to consider awarding Fisher a contract for border wall construction. One official said that Trump had to be reminded he could not just "pick a winner" and that many had doubts about Fisher's ability to handle the project.

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In a statement provided to NBC News after news of the inspector general's investigation surfaced, a spokesperson for Fisher Sand & Gravel said: "Fisher is looking forward to the opportunity to work with the Army Corps of Engineers on this important project, to build 31 miles of border fence near Yuma, Arizona. We are excited to show our high quality work and this project gives us an opportunity to demonstrate the caliber of work our team has delivered to our customers for six decades, while helping to secure our southern border."

Chip Unruh, a spokesman for Reed, said, "If President Trump personally and repeatedly pressured the Army Corps of Engineers to steer any contract to a politically connected firm, it would be extremely inappropriate and possibly illegal."

"Senator Reed is asking GAO to take a nonpartisan look at the awarding of all border-related construction to ensure all contracting and procurement laws were followed without any favoritism," he added.