Special counsel Robert Mueller has contacted at least seven people associated with Roger Stone, President Trump’s former election campaign adviser, during the course of his investigation into Russia’s role in the 2016 race, ABC News reported Friday.

Interviews with multiple witnesses and other individuals who claimed to be contacted by Mr. Mueller’s team suggest the special counsel’s probe is aggressively looking for evidence that would indicate whether persons associated with the president, especially Mr. Stone, a campaign adviser through 2015, colluded with Russia during the race, ABC reported.

Sources who said they were contacted by the special counsel’s office indicated that Mr. Mueller’s team is particularly interested in whether anyone involved in the Trump campaign knew during the race that Russian government hackers had infiltrated Democratic targets and pilfered emails ultimately published by WikiLeaks, the report said.

Russian state-sponsored hackers breached both the Democratic National Committee and the personal email account of John Podesta, Democratic candidate Hillary Clinton’s campaign chairman, and subsequently stole sensitive correspondence released by WikiLeaks in 2016, U.S. intelligence officials previously concluded.

The thefts and disclosures of Democratic emails were part of a Kremlin-authorized attack targeting the race and Mrs. Clinton’s campaign in particular, according to U.S. officials.

The Department of Justice announced charges following publication of ABC’s report Friday against 12 Russian military intelligence officials implicated in the hacks.

Mr. Mueller, a former FBI director, was appointed in May 2017 to investigate Russia’s alleged involvement, including any potential collusion between the Trump campaign and Moscow.

Mr. Stone, 65, successfully predicted the release of Democratic documents by WikiLeaks during the race and previously claimed to be in contact with the website’s publisher, Julian Assange.

“I never received anything including allegedly hacked emails from WikiLeaks or Julian Assange or the Russians or anyone else,” Mr. Stone told ABC News. “[I] never passed them on to Donald Trump or the Trump campaign or anyone else.”

Individuals close to Mr. Stone who said they were contacted by Mr. Mueller’s office include Jason Sullivan, his former social media consultant; Andrew Miller, a longtime associate; Randy Credico, a radio host and comedian who personally met with Mr. Assange at his residence in London during the race; and fellow former Trump campaign advisers Sam Nunberg and Michael Caputo. John Kakanis, Mr. Stone’s driver and accountant, was subpoenaed to appear before the special counsel, Reuters previously reported.

“CNN reports Mueller probing my personal finances. Reuters reports Mueller subpoenas my current and former associates and now clear my e-mail, text and phone all monitored. My crime? Supporting @realdonaldtrump for President!” Mr. Stone said in a social media post this week.

The special counsel’s office declined to comment when reached by The Washington Times.

Russia has denied hacking U.S. targets during the 2016 race, and Mr. Assange previously claimed his source was “not the Russian government.” James Clapper, the former director of national intelligence at the time of the election, said last month, meanwhile, that U.S. officials identified an individual suspected of serving as a conduit between Russian hackers and WikiLeaks.