The Republican chairman of the US Senate intelligence committee will step down while an insider trading inquiry is carried out.
Richard Burr of North Carolina said he had decided to do so because he did not want the investigation to distract the committee from its work.
Mr Burr’s phone has been seized by the FBI as part of the inquiry.
The senator, who denies wrongdoing, allegedly used inside information to avoid market losses from coronavirus.
He declined a request for comment.
Mr Burr and his wife sold as much as $1.7m (£1.4m) of equities in February, just before markets plunged on fears of an economic crisis.
It is illegal for members of Congress to trade based on non-public information gathered during their official duties.
Republican Senators Kelly Loeffler of Georgia and James Inhofe of Oklahoma, as well as Democratic Senator Dianne Feinstein of California, also reportedly sold holdings before the downturn, but are not confirmed to be under investigation.
Ms Feinstein said she had answered questions from the FBI regarding trades made by her husband, however.