A Republican US senator stepped down from a key committee leadership role in Congress on Thursday after his phone was seized overnight by investigators with a warrant looking into allegations that he used private briefings as inside information to dump shares before the market plummeted over the coronavirus crisis. Senator Richard Burr of North Carolina will “step aside” from his post as the chair of the Senate intelligence committee, the majority leader, Mitch McConnell, a fellow Republican of Kentucky, announced on Thursday afternoon. “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. 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,” at statement from McConnell said. Burr’s phone was seized by the FBI on Wednesday night, when investigators served him a warrant at his Washington home amid an ongoing investigation into whether he engaged in insider trading. Burr previously denied he had kept the public in the dark about the scale of the threat of coronavirus and also denied insider trading, saying he was relying on publicly available information when he dumped stock as the pandemic hit the US. Burr and his wife sold between around $628,000 and $1.7m in more than 30 separate transactions in late January and mid-February. Burr faced calls for his resignation when the news emerged in late March. Burr denied any impropriety and called for an ethics investigation on Capitol Hill in order to establish his innocence. Several of the stocks he and his wife sold were in companies that own hotels and followed senators receiving confidential briefings on the seriousness of the approaching pandemic even as the public was not yet fully aware of what was about to hit the US. More than 80,000 Americans died of Covid-19 between 11 March and 11 May, and the death toll continues to rise. Burr said in late March: “I relied solely on public news reports to guide my decision on the sale of stocks February 13,” he said in a statement. He told reporters at the US Capitol on Thursday he decided to step aside because he did not want the investigation to distract the intelligence committee from its work. “I thought this was the best thing to do,” Burr said. The warrant marked a significant step-up in the investigation. Donald Trump said, as he departed the White House for a visit to Pennsylvania, that he did not know anything about Burr’s decision, but added: “That’s too bad.” A senior justice department official said the FBI did not conduct a raid, but paid a visit to Burr’s home to collect his cellphone. Approval of the warrant – a significant development because it was served on a sitting senator – was obtained at the “highest levels” of the justice department, the official said. Reuters contributed reporting