WASHINGTON ― The FBI director confirmed the existence of an investigation into possible ties between associates of President Donald Trump and Russian government officials.

James Comey’s formal confirmation of the probe on Monday follows months of news reports quoting anonymous government officials discussing the FBI-led, multi-agency probe into communications between Trump allies and Moscow in the lead-up to the 2016 election. Comey is the first to publicly confirm those reports.

“I have been authorized by the Department of Justice to confirm that the FBI, as part of our counterintelligence mission, is investigating the Russian government’s efforts to interfere in the 2016 presidential election,” Comey told the House Intelligence Committee. “That includes investigating the nature of any links between individuals associated with the Trump campaign and the Russian government, and whether there was any coordination between the campaign and Russia’s efforts.”

The FBI has been investigating links between the Trump team and Russian officials since July, Comey told the House panel ― meaning the probe was underway during the height of an alleged effort by Moscow to tip the scale in favor of Trump during the 2016 election. He declined to speculate on how long it would take to conduct the investigation, but suggested that it wasn’t nearing completion. The eight-month period in which the investigation has been ongoing is a “fairly short period of time” for a counterintelligence investigation, he said.

The House Intelligence Committee is one of two congressional committees investigating Moscow’s role in last year’s presidential race.

The intelligence community publicly shared its assessment in January that the Russian government hacked Democratic entities and operatives and released damning information with the goal of helping Trump win the election. But the assessment did not indicate whether Trump and his campaign team were aware of or complicit in Moscow’s operations.

Lawmakers have pushed law enforcement and intelligence officials to respond to repeated queries about ties between Trump associates and Russian intelligence. Comey, to the frustration of several lawmakers, has insisted he cannot publicly discuss the possible existence of an ongoing investigation. (Comey did, however, disclose information to lawmakers related to an investigation into Democratic presidential candidate Hillary Clinton’s email server days before the election. His letter to lawmakers was quickly leaked.)

But the FBI director has faced mounting pressure to speak publicly about the situation, amid a relentless series of leaks about seemingly bizarre communications between high-level Trump aides and Russian intelligence officials.

Sen. Tim Kaine (D-Va.), who was Clinton’s running mate in her presidential bid last year, said on Wednesday that he expected Comey to announce publicly that the FBI is looking into the White House’s possible ties to Russia.

“As you know, our practice is not to confirm the existence of ongoing investigations, especially those investigations that involve classified matters,” Comey said Monday. “But in unusual circumstances, where it is in the public interest, it may be appropriate to do so. This is one of those circumstances.”

This article has been updated with Comey’s quotes and details from the hearing.