WASHINGTON (Reuters) - The U.S. Office of Special Counsel is investigating whether Interior Secretary Ryan Zinke broke the law when he gave a speech to a professional hockey team owned by a political donor in June, the agency said on Tuesday.

FILE PHOTO: U.S. Interior Secretary Ryan Zinke (C) talks to National Park Service Rangers, while traveling for his National Monuments Review process, in Boston, Massachusetts, U.S., June 16, 2017. REUTERS/Brian Snyder/File Photo

Zinke is already being investigated by the Interior Department’s inspector general in connection with his travels and the use of private charter flights, amid heightened scrutiny into private plane use by administration officials.

The Campaign for Accountability complained last week that a speech Zinke gave on June 26 to the Vegas Golden Knights, a National Hockey League team based in Las Vegas, violated the Hatch Act barring executive branch employees from engaging in political activity.

The team is owned by Bill Foley, chairman of Fidelity National Financial Inc and a donor to Zinke’s congressional campaigns.

The Office of Special Counsel’s Hatch Act unit, which is independent from the Justice Department, said in an email to Daniel Stevens, executive director of the Campaign for Accountability, that it received its Hatch Act complaint “and will open a case file to address this matter.”

A spokeswoman for the agency declined to comment on the case.

Interior Department officials said the speech did not violate any laws, rules or regulations.

Melinda Loftin, the Interior Department’s designated ethics official and Edward Keable, director of Interior’s departmental ethics office, said in a joint statement that Zinke’s use of chartered flights and engagements were cleared by ethics and legal departments.

“The trip - including the Secretary’s address to the hockey developmental squad - was completely compliant with all applicable laws, rules, and regulations,” they said.

On Friday, former Health and Human Services Secretary Tom Price resigned after an outcry over his use of costly private charter planes for government business.

The Campaign for Accountability questioned Zinke’s travel.

“Contrary to the conclusion drawn by Interior officials, a trip to offer a motivational speech to a hockey team does not appear to fall within the mission of the Department of Interior - ‘protecting America’s Great Outdoors and Powering Our Future,’” the watchdog group wrote.

In June, the Office of Special Counsel determined that Trump’s social media director Dan Scavino violated the Hatch Act in April in calling for Trump supporters to defeat a Republican congressman at the polls.