The incident took place after Metz went 1-0 in front midway through the first-half at Stade Saint-Symphorien, with the first device landing in the six-yard box and knocking Lopes to the ground.
As players and medical staff rushed over to help another firecracker landed next to Lopes and exploded, catching the goalkeeper and a club doctor.
The referee, Lionel Jaffredo, subsequently took the players off the pitch, and the match was abandoned after a further 45-minute delay. Lyon later tweeted to say Lopes was being assessed in hospital.
The Ligue de Football Professionnel, the governing body, confirmed it would be conducting an investigation, saying in a statement: “The LFP regrets this incident, and will be uncompromising in dealing with it.”
Speaking immediately after the game, Lyon’s president, Jean-Michel Aulas, said: “At best, he suffered very significant tinnitus. He has no balance and doesn’t really know where he is. At worst, his eardrum may be affected.
“This is so serious, so shameful. Security must be provided by the host club. We saw things that are unacceptable and unthinkable. I expect a strong reaction from the LFP and FFF [Fédération Française de Football].”
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