The Interior Department’s Office of the Inspector General (OIG) says it has begun a “preliminary investigation” into reports that Secretary Ryan Zinke Ryan Keith ZinkeTrump extends Florida offshore drilling pause, expands it to Georgia, South Carolina Conspicuous by their absence from the Republican Convention Trump flails as audience dwindles and ratings plummet MORE made phone calls pushing Alaska's senators to support a GOP healthcare bill or risk losing federal support for economic development efforts in their state.

“The OIG is undertaking a preliminary investigation into this matter,” Deputy Inspector General Mary Kendall said in a letter to two House Democrats on Thursday.

“We will advise you about what further action the results of this inquiry lead the OIG to take.”

The Interior Department did not immediately reply to a request for comment.

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Reps. Frank Pallone Jr. (D-N.J.) and Raúl Grijalva (D-Ariz.) had asked the Inspector General and other government investigators to probe Zinke’s calls to Alaska Sens. Lisa Murkowski Lisa Ann MurkowskiSenate Republicans face tough decision on replacing Ginsburg What Senate Republicans have said about election-year Supreme Court vacancies McConnell says Trump nominee to replace Ginsburg will get Senate vote MORE (R) and Dan Sullivan (R) ahead of last week’s vote on a GOP healthcare bill.

Zinke reportedly threatened obstructing federal economic development work in the state if Murkowski didn’t drop her opposition to the bill. She ended up voting against every GOP effort to repeal ObamaCare last week.

Murkowski has downplayed the incident and Zinke has shrugged it off, saying it’s “laughable” that he would threaten Alaska over healthcare.

On Thursday morning, Zinke tweeted a picture of the pair drinking beers together, calling Murkowski a “friend.”