Mikel Arteta says Pablo Mari "seems to be okay" after he was stabbed in an incident near Milan, while Arsenal said they have been told the defender, who is on loan at Monza, is "not seriously hurt".
The Spanish centre-back was one of several people injured in the disturbing scenes at a supermarket in Carrefour, Serie A club Monza confirmed on Thursday.
Arteta, whose side were defeated in Europa League action against PSV, issued a brief comment on the situation when speaking to the media after the game.
"I just found out," he said. "I know that [Arsenal technical director] Edu has been in touch with his relatives, and that he's in hospital, and he seems to be okay.
"But I don't know, I will have a briefing now about the situation, what happened, and obviously we will be in touch with him, and hopefully he's okay."
Arsenal issued a club statement, explaining they had been in touch with Mari's agent.
"We are all shocked to hear the dreadful news about the stabbing in Italy, which has put a number of people in hospital including our on-loan centre-back Pablo Mari," it read.
"We have been in contact with Pablo's agent who has told us he's in hospital and is not seriously hurt.
"Our thoughts are with Pablo and the other victims of this dreadful incident."