Washington (CNN) Congressional investigators are examining whether Attorney General Jeff Sessions had an additional private meeting with Russia's ambassador during the presidential campaign, according to Republican and Democratic Hill sources and intelligence officials briefed on the investigation.

Investigators on the Hill are requesting additional information, including schedules from Sessions, a source with knowledge tells CNN. They are focusing on whether such a meeting took place April 27, 2016, at the Mayflower Hotel in Washington, DC, where then-candidate Donald Trump was delivering his first major foreign policy address. Prior to the speech, then-Sen. Sessions and Russian Ambassador Sergey Kislyak attended a small VIP reception with organizers, diplomats and others.

In addition to congressional investigators, the FBI is seeking to determine the extent of interactions the Trump campaign team may have had with Russia's ambassador during the event as part of its broader counterintelligence investigation of Russian interference in the election.

The FBI is looking into whether there was an additional private meeting at the Mayflower the same day, sources said. Neither Hill nor FBI investigators have yet concluded whether a private meeting took place -- and acknowledge that it is possible any additional meeting was incidental.

"The Department of Justice appointed special counsel to assume responsibility for this matter," Department of Justice spokeswoman Sarah Isgur Flores said in a statement to CNN. "We will allow him to do his job. It is unfortunate that anonymous sources whose credibility will never face public scrutiny are continuously trying to hinder that process by peddling false stories to the mainstream media. The facts haven't changed; the then-Senator did not have any private or side conversations with any Russian officials at the Mayflower Hotel."