Team barred from competition after fan attack on rival players

River Plate's players (in red) try to take cover as they leave after their Copa Libertadores soccer match against Boca Juniors was suspended in Buenos Aires early May 15, 2015. [Photo/Agencies]

The attack left several players rubbing their eyes in agony as teammates desperately threw water in their faces to try to relieve the pain.

Doctors said four players suffered first-degree burns.

Media reports initially said the substance was pepper spray, but Boca club president Daniel Angelici said that was incorrect.

"It wasn't pepper spray, it was a toxic liquid," he said.

Television images showed a Boca fan with his face covered, apparently introducing something into the inflatable tunnel from the seating area behind it.

Prosecutors investigated the incident on the basis of that footage. They also analyzed the jerseys of the burned players to determine exactly what the substance was, and impounded the tunnel for analysis.

Boca's iconic stadium, the Bombonera, was closed Friday morning after the previous night's mayhem, which commentators said marked a new low for Argentina's violence-plagued soccer matches.

"If there was any dignity left in Argentine soccer, it was torn to shreds last night at the Bombonera," said an editorial in newspaper Pagina/12. "Soccer and its leadership have hit bottom."