WASHINGTON — The Treasury Department on Thursday fined Exxon Mobil $2 million for violating sanctions that the United States imposed on Russia in 2014 while Rex W. Tillerson, now the secretary of state, was the oil company’s chief executive.

The penalty was relatively small for the Treasury and a blip on Exxon’s mammoth balance sheet, but it came as controversy over Russia policy has engulfed Washington. The Trump administration is facing questions about Russia’s intervention in the 2016 election, and Congress has considered stiffening sanctions out of concern that President Trump will try to ease those already in place.

The move also underscores concerns over Mr. Tillerson’s deep business connections in Russia.

“Exxon Mobil demonstrated reckless disregard for U.S. sanctions requirements,” the Treasury said in a report announcing the penalty. “Exxon Mobil caused significant harm to the Ukraine-related sanctions program.”

Hal Eren, a former official in Treasury’s Office of Foreign Assets Control, said the fine showed that the department’s staff members would not be cowed.