The Department of Justice inquiry into the origins of the Russian probe into election interference and collusion has become a criminal investigation.
The escalation was reported by the New York Times on Thursday.
Shifting the inquiry into a criminal investigation would allow prosecutor John H. Durham to subpoena documents and witnesses, and also to convene a grand jury.
The Times reported that it was unclear what specific crime would be investigated.
Allies of the president have accused Democrats of illegally using the powers of government to surveil members of the Trump campaign in 2016 for political purposes. Those defending the investigation say it was an appropriate response to suspicions that the Trump campaign might have colluded with the Russian government.
"Spying on a campaign is a big deal,"Attorney General William Barr said to lawmakers in April. "I think spying did occur. The question is whether it was adequately predicated."
President Donald Trump has called the accusations and investigation a "witch hunt."
Rep. Mark Meadows (R-N.C.) responded positively to the development via his social media account.
"NYT report: DOJ opening a criminal investigation into the spreading of the Russian collusion conspiracy," he tweeted. "If true, this shows Bill Barr is doing EXACTLY his job: following the facts."
"Those who damaged America and broke the law to spread this hoax are about to face accountability," he added.