Alexandre Lacazette struck twice, including a penalty, while Nicolas Pepe and Bukayo Saka also found the net in the quarter-final second leg to set up a last-four clash with Villarreal.
Arsenal said they are taking reports striker Alexandre Lacazette inhaled nitrous oxide from a balloon "seriously" and will deal with the matter internally.
Arsenal manager Unai Emery insisted his side's Europa League semi-final against Valencia is still "50-50" despite the Gunners taking a 3-1 first leg lead to Spain.
Arsenal returned to winning ways with a 2-1 victory over bottom side Huddersfield Town on Saturday, but remain the only side without an away clean sheet in the Premier League this season.
Alexandre Lacazette's late goal earned Arsenal a 1-1 draw with Liverpool on Saturday and stopped the visitors moving three points clear at the top of the Premier League table.
The French moved from his childhood club, Lyon, to join Arsenal in summer 2017.
Arsène Wenger’s employment as the head coach of Arsenal remains conditional.
Both players previously faced each other in the French League, as Lacazette played for Lyon while Aubameyang was playing for their local rivals, Saint Eteinne.
French striker Alexandre Lacazette explained why he agreed to move to Arsenal despite Atletico Madrid’s attempts to sign him last summer.
Many rumors linked Thomas Lemar with leaving Monaco to join Arsenal, but the player decided to stay with his club.
Lacazette and Coquelin played together with France national team in the 2010 UEFA European U-19 Championship and the 2011 FIFA U-20 World Cup.
Arsenal FC completed their second signing on July 5 after agreeing to Alexandre Lacazette’s personal terms.
Lyon reached an agreement to sign the young striker Mariano Diaz from Real Madrid.
It will cost Arsenal £ 60 million to sign Lacazette