The Justice Department’s inspector general is investigating the Trump administration's decision to open an antitrust probe of four automakers that had sided with California in a feud over the state’s strict vehicle emissions standards, Sen. Sheldon Whitehouse (D-R.I.) said Wednesday.

“I believe the inspector general is investigating this matter,” Whitehouse said at a hearing on the nomination of Jonathan Kanter, President Joe Biden’s pick to helm the DOJ’s antitrust division. The IG's office has not announced that it was looking into the Trump-era probe, which Whitehouse and Gov. Gavin Newsom lambasted at the time as politically motivated.

The case: The Trump DOJ opened its inquiry into Ford, Volkswagen, Honda and BMW in 2019, investigating whether they illegally coordinated when they entered an agreement to follow California's limits on auto emissions. The probe came as the Trump administration was fighting on multiple fronts to stop the state from thwarting the president's efforts to roll back clean air rules.

The antitrust division later closed the probe without taking any action.

Last summer, a DOJ whistleblower testified before Congress that the probe was rushed, unusual and launched despite objections from career staff the day after then-President Donald Trump tweeted critically about the deal. Trump denounced the leaders of the "politically correct Automobile Companies" as "foolish" for opposing his push for laxer regulations.

Trump DOJ officials, including former antitrust division leader Makan Delrahim, denied that the probe was motivated by political bias.

Whitehouse’s interest: The Rhode Island senator has repeatedly pushed the Justice Department for information on the antitrust probe. At Wednesday’s hearing, Whitehouse said he was concerned that the inspector general’s investigation wouldn’t extend to possible White House’s involvement.

A DOJ inspector general probe “stops as soon as the White House says it stops,” he said. “If there were violations of the Department of Justice and White House counsel policy regarding contacts between the Department of Justice and White House, that would be an appropriate use of this committee’s oversight inquiries.”