Paraguay international Salvador Cabanas is in a critical condition after being shot in the head on Sunday night, Mexico City's attorney general has confirmed.
Cabanas, 29, was shot after an incident in the city.
The Club America striker was taken to a hospital intensive care unit.
Mexico City attorney general Miguel Angel Mancera says: “We don't clearly know the motive behind the injury.
“According to an initial report it was a shot from a firearm with a frontal entry point and without exit.
“The player is conscious but he has a heart problem which they're trying to stabilise.
“We're waiting to see what those arrested have to say.
“It seems that the attack happened in the bathroom of the bar.”
Cabanas is one of Paraguay's most highly-rated players and was part of their World Cup squad in Germany.
Sunderland manager Steve Bruce recently revealed he was interested in bringing the striker to the Barclays Premier League. Cabanas' international team-mate Paulo Da Silva is currently at Sunderland.
The striker, who has scored over 100 times in the Mexican top-flight, has netted 18 goals in 24 matches this season.
Club America president Michel Bauer revealed the forward was undergoing surgery. Bauer added that he believed the attack to have been unprovoked, having spoken to Cabanas' wife who was present with the striker at the time of the attack.
“He arrived conscious and responded well to the questions they asked him as he was going into hospital,” Bauer said. “It's a key point that can be encouraging, but until further notice we cannot speculate on anything at all.
“They wanted to assault him. I can confirm that that is what his wife has said, that it was an assault.
“There was no shoot-out nor any quarrel.”