The U.S. Transportation Department’s inspector general said this week it had twice asked the Justice Department under President Trump to investigate then-Secretary of Transportation Elaine Chao.

The DOJ declined both times -- the U.S. Attorney’s Office for the District of Columbia on Dec. 16, 2020, and the DOJ’s Public Integrity Section the next day.

In a letter to House Transportation Committee Chairman Peter DeFazio, D-Ore., the inspector general’s office explained its findings.

CAPITOL RIOTING FORCES TRANSPORTATION SECRETARY ELAINE CHAO TO RESIGN

The IG alleged that Chao used her position to benefit her family’s shipping company and used her taxpayer-funded staff for personal tasks.

Then-Transportation Secretary Elaine Chao speaks to reporters outside the West Wing of the White House following President Donald Trump's signing of the executive order supporting the transition of active duty service members and military veterans into the Merchant Marine, Monday, March 4, 2019, in Washington. (AP Photo/Manuel Balce Ceneta) (AP)

"A formal investigation into potential misuses of position was warranted," deputy inspector general Mitch Behm wrote in the letter.

Chao is married to Senate Minority Leader Mitch McConnell, R-Ky. She has denied any wrongdoing.

Her family’s company, operated by her father and sisters, does much of its business with China. It attracted attention in 2016 when Colombian authorities found 90 pounds of drugs on one of its vessels, prompting the moniker "Cocaine Mitch," which Sen. McConnell turned against his detractors and used to raise campaign funds – selling $35 T-shirts satirizing the phrase.

The watchdog raised ethical concerns over several instances – including one where Chao allegedly instructed subordinates to contact the Homeland Security Department to check on the status of a work permit application for a student who was a recipient of her family’s philanthropic foundation.

She also allegedly had the DOT’s public affairs office help market her father’s biography and edit his entry on Wikipedia.

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The DOJ at the time said that while there may have been evidence of ethical violations, there was none to support criminal charges.

The IG's letter also noted that investigators could not corroborate allegations that Chao imporoperly steered federal funds to her home state of Kentucky. It also cleared her of conflict of interest allegations regarding stock in a stone and asphalt producer.

Chao resigned from her position in protest of the Jan. 6 Capitol riot.

The Associated Press contributed to this report.