"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," UEFA said in a statement.
"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."
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The European meetings between the clubs was marred by vile chants about the 1958 Munich air crash -- which killed 23 people including eight Manchester United players -- and the Hillsborough disaster in which 96 people lost their lives during the 1989 FA Cup semi-final between Liverpool and Nottingham Forest.
The Mersyside club advanced to the Europa League quarter-finals following a 3-1 aggregate win over Manchester United. Liverpool will next face manager Juergen Klopp's former club Borussia Dortmund.
(Reporting By Arnab Paul in Bengaluru, editing by Pritha Sarkar)
