WASHINGTON — Senator Richard M. Burr, Republican of North Carolina, temporarily stepped down as chairman of the Senate Intelligence Committee on Thursday, a day after F.B.I. agents seized his cellphone as part of an investigation into whether he sold hundreds of thousands of dollars’ worth of stocks using nonpublic information about the coronavirus.
The seizure and an accompanying search for his electronic storage accounts, which were confirmed by an investigator briefed on the case, represented a significant escalation of the inquiry by the Justice Department and the Securities and Exchange Commission. Mr. Burr decided to step aside “during the pendency of the investigation” on Thursday and informed Senator Mitch McConnell, Republican of Kentucky and the majority leader.
“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,” Mr. McConnell said.
Mr. Burr sold the stock in mid-February before the market cratered and while President Trump and some supporters were downplaying the threat of the virus. At the same time, Mr. Burr was receiving briefings and involved in conversations suggesting the country faced a burgeoning health crisis that could hurt the economy.