WASHINGTON (Reuters) – U.S. Energy Secretary Dan Brouillette was returning to Washington on Friday, cutting short a trip to the Midwest after two of his security aides tested positive for the coronavirus, a Department of Energy spokeswoman said.

Brouillette’s COVID-19 test results have been negative and he is not exhibiting any symptoms but “out of an abundance of caution, the Secretary and traveling staff will be returning by vehicle to Washington and following CDC guidance,” department spokeswoman Shaylyn Hynes said on Twitter.

Brouillette has been traveling frequently to several battleground states ahead of the Nov. 3 presidential election. On Tuesday he visited Oak Ridge, Tennessee, and spoke at an event with Senator Lamar Alexander and U.S. Representative Chuck Fleischmann and Governor Bill Lee, all Republicans.

On Wednesday, Lee said he would quarantine at home after a member of his security staff tested positive for the coronavirus.

On Thursday Brouillette toured western Pennsylvania, an energy rich state, visited frequently by President Donald Trump and his Democratic challenger, Joe Biden. In Johnston, Brouillette visited Concurrent Technologies Corporation, a nonprofit scientific research and development group. In Erie, he visited a local union hall meeting with plumbers, steamfitters and boilermakers.

On Friday Brouillette had been scheduled to visit Ohio to participate in a roundtable with leaders across the energy industry at Youngstown State University and then meet local officials backing a petrochemical project in Belmont County.

More than 217,000 people in the United States are reported to have died from the novel coronavirus, more than in any other country.

U.S. Environmental Protection Agency Administrator Andrew Wheeler and Interior Secretary David Bernhardt, two other members of Trump’s administration who work on energy and environment issues, have also been traveling frequently ahead of the election.