Mehdi Rahmoun (left) appeared to be struck by an object thrown from the stands
The Ligue 1 match between local rivals Saint-Etienne and Lyon was suspended for around 40 minutes after an assistant referee was hit by an object thrown from the stands.
Visitors Lyon, trailing 1-0, were about to take a 44th-minute throw-in when Mehdi Rahmouni held his head after being hit by something.
French newspaper L'Equipe said Rahmouni had been hit by a coin thrown from the stands.
Lyon's medical team treated Rahmouni before referee Francois Letexier led the players and officials left the pitch.
Play did eventually resume after a lengthy break, with Saint-Etienne going on to win 2-1.
"We're going to restart the game because the assistant referee feels up to restarting," Noel Mannino, the league matchday representative, told AFP.
"At the next incident, the match will be stopped for good."
Lyon fans were banned from travelling to the match because of previous incidents.
Saint-Etienne had previously been threatened with having two ends of the ground closed after recent "massive use of pyrotechnic devices and verbal abuse".
In March, their match at Montpellier was abandoned after home fans threw flares on to the pitch and part of a stand caught fire.
