(Courthouse News) The Interior Department’s inspector general has launched an investigation into a Montana real estate deal involving Secretary Ryan Zinke and the chairman of Halliburton.

The investigation was first reported by Politico, which said it based its reporting on a letter sent to Capitol Hill on Wednesday.

Democrats had called for an investigation of the commercial real estate development deal, which reportedly involved Zinke and a group of developers including Haliburton chairman David Lesar in Zinke’s hometown of Whitefish, Montana.

“You’ve expressed special concern about the reported funding by a top executive at Halliburton and assuring decisions that affect the nation’s welfare are not compromised by self-enrichment,” wrote Mary Kendall, deputy inspector general of the Interior Department.

Kendall sent the letter to Rep. Raul Grijalva, D-Arizona. In it, Kendall also confirmed the formal investigation was opened on Tuesday.

In a letter sent to the inspector general’s office in June, Grijalva and fellow Democrat Reps. Donald McEachin of Virginia and Jared Huffman of California said they had discovered emails that showed Zinke met with Lesar and Montana developer Casey Malmquist in his Interior Department office on Aug. 3, 2017.

According to Politico, the development deal was approved by the Whitefish City Council in January 2018.

The Democrats asked the inspector general to determine whether Zinke unlawfully used his office for personal gain.

A representative from Kendall’s office did not immediately respond to request for comment on Thursday, nor did a representative from the Interior Department. But in recent weeks, Zinke has dismissed allegations of impropriety around the deal.

According to multiple media reports in June, Zinke confirmed last year’s meeting with Lesar and said the two met to discuss Zinke’s recent resignation from the Great Northern Veterans Peace Park Foundation in Whitefish. The men also discussed land the foundation controls, Zinke said.

A month after the August 2017 meeting with Lesar, Zinke’s wife Lola approved an agreement allowing Lesar and other land developers to break ground on parking lot earmarked for a redevelopment project.

Thursday’s letter by the watchdog prompted Grijalva to describe Zinke’s handling of the Interior Department as “more about him waving his own flag above the building and doing personal business deals with his friends instead of protecting public lands and improving our environmental quality.”

Kendall’s office is also currently investigating Zinke and fellow appointees for a lobbying deal related to Native American tribes. The watchdog is currently reviewing whether Zinke and others caved to MGM Resorts International lobbyists by stalling the internal review process for gaming applications from several tribes.

Redacted emails obtained through the Freedom of Information Act revealed career staffers at Interior shared emails labeled as “approval letters” for the tribes just two days before suddenly reversing course and halting the application process.

While the applications weren’t rejected, the tribes were left with no other option but to wait on Zinke.

Zinke has also been the focus of other investigations, including a review of his use of charter flights and speeches he gave to political donors. Ultimately, Kendall found the flights did not violate any laws though officials were unable to conduct a complete review since Zinke failed to mention the role a major donor played in one of the trips.

News of the investigation was one of two blows to the department: The House voted down an amendment that would have increase Kendall’s office budget by $2.5 million.