Pilot Flying J is a multibillion-dollar chain of more than 650 truck stops and convenience stores owned by the family of Tennessee Gov. Bill Haslam.
An FBI official said the action also involved the Internal Revenue Service, but did not offer details, The (Nashville) Tennessean reported Tuesday, adding FBI officials, some wearing bulletproof vests, were seen at the company's headquarters Monday.
A spokesman for the Knoxville Police Department said police were asked to help execute a search warrant.
Bill Killian, U.S. attorney for the Eastern District of Tennessee, said an investigation was ongoing, but declined to elaborate.
A statement from Pilot Flying J President Jimmy Haslam said the company is cooperating with the federal investigation.
"I believe and trust there has been no wrongdoing," Haslam said.