The Interior Department’s inspector general has opened an investigative complaint regarding Secretary Ryan Zinke’s involvement in a Montana land development deal backed by the chairman of the oil services firm Halliburton, according to a letter sent to three Democratic lawmakers.

In the letter sent to Reps. Raúl M. Grijalva (Ariz.), A. Donald McEachin (Va.) and Jared Huffman (Calif.) on Wednesday, Interior Deputy Inspector General Mary L. Kendall said that her office will examine Zinke’s “reported ongoing involvement in and use of taxpayer resources to advance land developments in Whitefish, Montana.” Last week, Politico reported that Zinke has continued to be involved in discussions over the development of land near his hometown that is backed by David J. Lesar, Halliburton’s chairman.

The oil services giant’s operations are directly affected by many of the Interior Department’s policies, including regulations on how oil and gas drilling must be conducted, and which public lands and federal waters are open to exploration and development.

The real estate deal involves land owned by a foundation connected to Zinke and his wife, Lola Zinke. Interior officials say that Ryan Zinke resigned as the foundation’s president and board member upon being selected to serve in President Trump’s Cabinet; Lola Zinke now serves as its president.

The development, known as 95 Karrow, is set to include shops as well as a microbrewery, which Zinke himself proposed half a dozen years ago. The Zinkes own multiple parcels of land in proximity to the planned project.

Zinke has continued to met with Lesar, his son and the lead project developer, Casey Malmquist, since taking office, according to department records. On Aug. 3, Zinke met with all three men in his office, took them on a private tour of the Lincoln Memorial and had dinner with them.

Malmquist confirmed in an interview with Politico that the group “discussed 95 Karrow at dinner” but not during the office meeting. In an email exchange in September, released under the Freedom of Information Act, Malmquist wrote the secretary about the development and solicited his input on its design.

“Ryan — our development plan and your park project are an absolute grand slam,” Malmquist wrote. “I have never been more excited about a development as I am about this one. … We are honored to be associated with you.”

In the emails, which Zinke appears to have forward to his assistant from a personal account, Malmquist told the secretary that he was “eager to learn more about you and your family’s vision” for the project.

“We are considering several names such as ‘Trestle View’, ‘Timber Town’, ‘Trestle Point’ etc. Please let us know if you have any ideas,” Malmquist wrote. “Thanks and I look forward to hearing from you.”

Neither Malmquist nor the Interior Department responded Thursday to requests for comment about the real estate deal.

Halliburton spokeswoman Emily Mir said in an email Thursday that the firm “does not comment on its executives’ personal investments outside the company.”

The three Democratic congressmen, all of whom sit on the House Natural Resources Committee, asked the IG to investigate the matter, writing in a letter last week that it raises “troubling questions about whether Secretary Zinke has used federal resources and his position as Secretary of the Interior for personal financial gain and whether he or other DOI staff is actively trying to cover it up.”

In her response, Kendall wrote that her office opened a complaint on the issue June 20, before receiving their letter. “We will review your concerns and specific questions during the course of the initial review,” she said.

As the inspector general’s office opened one probe, it concluded another. The watchdog bureau announced Thursday it found no sexual harassment while investigating an allegation against the top official at the National Park Service.

P. Daniel Smith admitted to investigators that he acted in a way “not appropriate for work” while telling a story in an Interior Department hallway about urination. But he denied that he “touched himself obscenely” as suggested by an anonymous letter sent to Zinke in March, according to a summary of that investigation released Thursday.

Smith’s job appears to be safe. Zinke “has a zero tolerance policy when it comes to sexual harassment and holds wrongdoers accountable for their actions,” according to a statement his office provided to The Washington Post. The secretary has repeatedly vowed to crack down on harassment across the Interior Department, which includes the Park Service. He fired four “senior leaders” for harassment last year.

But in this instance, his office said, “Neither the witnesses in the report, nor the IG, found this to be a case of sexual harassment.” In the letter that started the probe, the anonymous Park Service employee wrote to Zinke about how Smith “grabbed his crotch and his penis and acted out as though he was urinating on the wall” while relaying a story in January to another employee.

But investigators could not ask that employee to elaborate because she chose to remain anonymous.

“I wish I could come forward,” the worker wrote, “but retaliation is real.”