Manchester United could be hit with another UEFA charge after the governing body announced it was investigating reports of illicit chanting in their Europa League clash against Liverpool.
Both of the north-west giants last week found themselves subject to a host of disciplinary proceedings following disturbances during last Thursday's last-16 second-leg tie at Old Trafford.
However, only Liverpool were initially charged with illicit chanting, despite claims some sections of the United support chanted about the Hillsborough disaster in both legs.
UEFA said in a statement: "UEFA has recently been made aware of several reports concerning alleged illicit chanting on the occasion of the UEFA Europa League ties between Liverpool FC and Manchester United FC of 10 and 17 March 2016.
"As a result, a UEFA ethics and disciplinary inspector decided to investigate further and gather potential evidence.
"The two clubs have thus been asked to provide statements relating to the alleged incidents within 10 days."
Liverpool advanced to the quarter-finals of the competition with a 3-1 aggregate victory over Louis van Gaal's men.