Washington (CNN) Interior Secretary Ryan Zinke has mixed official business with political activities and visits home, raising questions about the appropriateness of the trips and whether any ethics rules have been violated.

Zinke's travel is under investigation by both the Office of Special Counsel and the Interior Department's inspector general.

Travel by Cabinet officials has been under the microscope since then-Health and Human Services Secretary Tom Price was found to take private flights costing hundreds of thousands of dollars and resigned. But it's not just the cost of private travel that has ethics officials looking at Zinke's schedule.

Just weeks after officially becoming interior secretary, Zinke traveled on March 30 to the US Virgin Islands for official business. He attended a series of meetings with local government officials and veterans as well as a Republican party fundraiser that cost between $75 to $5,000 to gain access.

In May, Zinke tacked on a political event to a multi-day work trip in Alaska. On May 31, after days of meeting with business leaders, government officials, veterans and native groups, Zinke attended a campaign reception for Republican Rep. Don Young of Alaska. Young's campaign spokesman, Matt Shuckerow, said Zinke was there for 15 to 20 minutes and he gave brief remarks.

"Everything associated with Congressman Young's event was done by the book," Shuckerow said. "Not only did the campaign seek out the guidance of the Interior Department's ethics personnel prior to the event, it took concerted efforts to follow their strict guidance."

Shuckerow also told CNN Zinke's attendance was not confirmed in advance or advertised to guests on invitations or other formal communications and, at the event, the secretary was not referred to by his title at his request. Shuckerow added, "There were no costs associated with entrance or attendance by guests." It is unclear if there were any other costs associated with getting Zinke to the event and who paid for it.

CNN has asked the Interior Department whether portions of the trip that involved political activities were allocated and subsidized by an entity other than the federal government. The agency has not responded.

Federal law does not ban political activity but it does limit certain political activities by federal employees, which is meant to ensure that programs are administered in a nonpartisan fashion and protect employees from political coercion in the workplace, according to the Office of Special Counsel's website.

Those trips are in addition to a widely reported trip to Las Vegas, where Zinke met with the Vegas Golden Knights hockey team, owned by billionaire businessman Bill Foley, whom Zinke called "a major donor" when he was running for Congress in 2014.

It remains unclear whether any laws were broken, but ethics watchdog groups say Zinke's official travel mixed with political activity are at the very least bad optics.

"To be a secretary of a department you would think the initial focus in the first year in office would be getting the department organized and initiatives taken care of," said Virginia Canter, the executive branch ethics counsel for Citizens for Responsibility and Ethics in Washington. "What's a bit unusual here is so quickly after getting into office Zinke is quickly engaged in political activity. It is a distraction."

In a joint statement, Melinda Loftin, director of the department's ethics office, and Edward Keable, deputy solicitor, write, "The Scheduling Office meets regularly with the Departmental Ethics Office and the Division of General Law to ensure that all travel is thoroughly reviewed and approved in advance and that it is fully compliant with all applicable laws, rules, and regulations."

Ethics experts say Zinke can engage in certain political activities if his title as secretary is not used and he does not use any government resources. Federal employees cannot fundraise but they can speak at fundraisers. There are no allegations that Zinke either used his title or raised funds

But the question ethics watchdogs are raising is whether it's a little too coincidental that his official duties are coinciding with his political activities.

"Is he using the official travel to subsidize his political activity?" asked Canter. "You have to follow a very specific formula to make sure if you're on official business the money is allocated in accordance with the regulations."

House Democrats who sit on the committee that oversees the Interior Department wrote a letter to the inspector general also raising concerns about Zinke's mix of political activities and official business.

Watchdogs question trips home

Ethics watchdogs question whether official business was scheduled in a way that would allow Zinke to frequently visit his home in Montana.

Records show of six trips to Zinke's home state at least three times included time at his house from March to August.

An Interior Department official calls such allegations "ridiculous," noting the state is full of department "lands, offices, and assets."

On March 9, Zinke took a 4:08 pm flight from Washington to an airport about 23 minutes from his Montana home, according to his Interior Department schedule. Once arriving in his home state, he spent the night at home. The next day he spent four hours at Glacier National Park which included meetings with park staff. His schedule says by 1:00 pm he was en route to return home where he spent the rest of the day. He left on the March 11 to make another stop in another part of Montana and then stayed overnight in Missoula.

On May 12, Zinke returned to Montana. Zinke's schedule says he had meetings with tribal leaders and energy producers and a horseback tour of a mine with Vice President Mike Pence on May 12. Later that evening, Zinke attended a rally for congressional candidate Greg Gianforte who was running for the seat Zinke left to lead the Interior Department. A picture tweeted from Zinke's official twitter account shows him with Pence and Gianforte with the caption "rallying the grassroots."

The next day Saturday, May 13, Zinke took a personal day, spending the night at his home in Whitefish. His schedule indicates he used a rental car that he paid for himself for the personal travel.

On the morning of June 27, Zinke was again in Whitefish where he gave a speech to the Western Governors' Association, a bipartisan group. That afternoon he visited the nearby Glacier National Park for a photo shoot with GQ magazine and an interview with Outside magazine, and later attended what his schedule notes was a "Wildlife Encounter Discussion." That evening Zinke would spend the night and next morning at his home in Whitefish, according to his schedule.