"I'm concerned about what happened but there was nothing contemporaneous that I'm aware of that is of great consequence," Biden told reporters during his visit to Ireland.
"There's a full- blown investigation going on … with the intelligence community, the Justice Department, and we're getting close … I don't have an answer," he stated.
Last week, media reported that a new trove of classified documents leaked online revealed that the US was conducting espionage not only on its opponents but also allies, which sparked deep concern among US officials, who think that the situation might endanger the US's sources and undermine important international ties.
All of the leaked documents reportedly were color printouts with text, graphics or maps, accessible to about 1,000 people prior to the incident.