Location, cellular and call record data revealed a call tying a Proud Boys member to the Trump White House, the official said. The F.B.I. has not determined what they discussed, and the official would not reveal the names of either party.

The connection revealed by the communications data comes as the F.B.I. intensifies its investigation of contacts among far-right extremists, Trump White House associates and conservative members of Congress in the days before the attack.

The same data has revealed no evidence of communications between the rioters and members of Congress during the deadly attack, the official said. That undercuts Democratic allegations that some Republican lawmakers were active participants that day.