The review is being conducted by Connecticut U.S. Attorney John Durham. The change in status gives Durham the power to subpoena witness testimony and documents, to impanel a grand jury and to file criminal charges, according to the New York Times, which first reported the shift.
President Donald Trump has long called the Russia investigation conducted by special counsel Robert Mueller a "witch hunt."
The evolution of the probe is sure to raise calls that Trump is using the Justice Department to go after his perceived enemies.
Democratic Reps. Adam Schiff, who is chairman of the House Intelligence Committee, and Jerrold Nadler, who heads the House Judiciary Committee, called the reports of a criminal investigation troubling.
"If the Department of Justice may be used as a tool of political retribution or to help the President with a political narrative for the next election, the rule of law will suffer new and irreparable damage," the lawmakers said in a statement.
A man in the Santa Clarita area north of L.A. was stunned by the proximity of the flames on a ridge during a television interview with NBC Los Angeles.
"Woah, Lord. What are we going to do?" the man identifying himself as James said as the sky filled with a smoky haze. "This is unbelievable. I’m about to leave — I can't stay," he added.
Parts of Northern California were also engulfed in flames.
The threat of wildfires prompted California's largest utility, Pacific Gas and Electric Corp., to pre-emptively shut off electricity to hundreds of thousands of people in Northern California on Wednesday.
The possible number of personnel that could be involved in security reinforcement at oil fields in the Deir ez-Zor region hadn't been determined, but "we're not talking thousands," the official said.
The operation, if approved, would be conducted alongside the mostly Kurdish Syrian Democratic Forces, the official said.
The United States announced earlier this month that it would withdraw its forces from northern Syria. The move was seen as a major blow to the Kurds who have been crucial U.S. allies in the war against ISIS.