The Justice Department is probing his stock trades amid pandemic briefings.

Republican Sen. Richard Burr has announced he will step aside from his position as chairman of the Senate Intelligence Committee amid a Justice Department investigation into stock trades he made prior to the market’s plunge from the spread of coronavirus.

“Senator Burr contacted me this morning to inform me of his decision to step aside as Chairman of the Intelligence Committee during the pendency of the investigation,” Senate Majority Leader Mitch McConnell said in a statement Thursday. “We agreed that this decision would be in the best interests of the committee and will be effective at the end of the day tomorrow.”

The announcement followed a dramatic escalation in the FBI’s probe of Burr. A senior Justice Department official confirmed that Burr provided his cellphone to investigators Wednesday after his lawyer was served with a subpoena.

The official said that the warrant was approved “at the highest levels” of the department, while not naming specific individuals who may have signed off.

Shortly after the news broke, Burr told ABC News’ Allison Pecorin on Capitol Hill that he’s cooperating with the investigation and has been“since the beginning.”

He said he stepped aside as Senate Intelligence Committee chairman to avoid the “distraction” from the panel’s work.

He wouldn’t further discuss details of the probe or his cell phone.

The Los Angeles Times first reported the news of the FBI’s seizure of Burr’s cell phone.

A lawyer for Burr has not responded to ABC News’ request for comment. The FBI declined to comment on the matter.

Burr has repeatedly denied any wrongdoing in his sale of up to $1.7 million in stocks on Feb. 13, with many trades involving industries hit hard in the wake of COVID-19’s spread throughout the U.S.

A spokesperson for Sen. Dianne Feinstein, D-Calif., confirmed separately Thursday that she was also asked “basic questions” recently by law enforcement related to stock transactions made be her husband.

“She was happy to voluntarily answer those questions to set the record straight and provided additional documents to show she had no involvement in her husband’s transactions,” the spokesperson said. “There have been no follow up actions on this issue.”

It is not clear whether the investigation of Burr’s or Feinstein’s activities includes stock sell-offs by some of their other fellow lawmakers during the same time period, including Sen. Kelly Loeffler, R-Ga. and Sen. Jim Inhofe, R-Okla.

All have denied that their stock activity had any connections to classified briefings that were provided to lawmakers at the time that had reportedly underscored the severity of COVID-19 and how it could affect the broader U.S. economy.

This is a developing story. Please check back for updates.