WASHINGTON — The Justice Department is examining communications between right-wing extremists who breached the Capitol and Roger Stone, a close associate of former President Donald Trump, to determine whether Stone played any role in the extremists’ plans to disrupt the certification of President Joe Biden’s electoral victory, a person familiar with the matter said Saturday.

Should investigators find messages showing that Stone knew about or took part in those plans, they would have a factual basis to open a full criminal investigation into him, according to the person, who spoke on the condition of anonymity to discuss a continuing inquiry. While that is far from certain, the person said, prosecutors in the U.S. attorney’s office in Washington are likely to do so if they can find that connection.

Stone, a self-described fixer for Trump, evaded a 40-month prison term when the former president commuted his sentence in July and pardoned him in late December. Stone had been convicted on seven felony charges, which included obstructing a House inquiry into possible ties between the Trump campaign and Russia’s efforts to interfere in the 2016 election. But that pardon does not protect Stone from future prosecutions.

Justice Department officials have debated for weeks whether to open a full investigation into Stone, the person said. While Stone spoke at an incendiary rally a day before the attack, had right-wing extremists act as his bodyguards and stood outside the Capitol, those actions themselves were not crimes.

But the FBI also has video and other information to suggest that in the days leading to and including the day of the assault, Stone associated with men who eventually stormed the building, said the person familiar with the inquiry. That has given investigators a window to examine communications to see whether Stone knew of any plans to breach the complex.

The New York Times has identified at least six members of the Oath Keepers, a far-right extremist group, who guarded Stone and were later seen inside the Capitol.

A Justice Department spokesperson declined to comment. Stone did not immediately respond to a request for comment. In a statement posted online this month, Stone denied any role in the “lawless attack.”