Rangers manager Steven Gerrard has called on Uefa to investigate claims Connor Goldson and Alfredo Morelos were struck by missiles during Thursday's 1-1 Europa League draw with Porto.
Defender Goldson insisted he was hit with objects thrown from the crowd and also said striker Morelos was struck as he celebrated his equaliser.
The draw at the Estadio do Dragao leaves Rangers second in Group G.
"It is something we don't like to see," Gerrard said.
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"I went in the dressing room after the game and it wasn't brought to my attention. It was only brought to my attention five minutes ago.
"We've got to think about the safety of the players. We've seen that on numerous occasions. That must stop.
"So I think Uefa need to look into that and try and deal with that."
Rangers return to Scottish Premiership duty at home to Motherwell on Sunday, having been replaced at the top by Celtic last weekend following a 1-1 stalemate at Hearts.
Gerrard wants a faster start from his team after they dropped points for the first time in five league matches.
"If you go into the game, certainly at Tynecastle against Hearts, and think you can just casually stroll into a match and you're not at your top level, you can be found out," Gerrard said.
"We certainly were in the opening 10 minutes. We can't afford that. We have to be better from the first whistle."