Toxicology tests have revealed that the irritant used to attack River Plate players during an Argentine "clasico" match at Boca Juniors' home stadium was a homemade concoction consisting of hot pepper sauce, cayenne pepper and acid, local media has reported.
That mixture, which is known as "mostacero" in prison culture and produces skin irritation and a burning sensation, was identified through analysis of wall stains at La Bombonera stadium, the Argentine news outlets said, citing sources close to the investigation, reports Efe.
The analysis ruled out an initial hypothesis that the players may have been mistakenly sprayed with pepper gas by police who responded to the disturbances.
The attack occurred on Thursday at La Bombonera during a round-of-16 match of the Copa Libertadores football competition pitting the two Buenos Aires-based arch-rivals.
River Plate players were preparing to take the field through an inflatable tunnel for the start of the second half when a hooded assailant threw the substance at the players, who emerged from the tunnel with teary eyes and irritated skin.
The attacker is believed to be a suspected hooligan known as "El Panadero", according to media outlets on Saturday, although Argentine authorities have not officially confirmed that.
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The security lapses and unruly crowd behavior made news worldwide and forced the suspension of the match.
It is now up to the South American Football Confederation to determine how to conclude the second leg of that round-of-16 clash of the Copa Libertadores, the continent's most prestigious club competition.
On Friday, Conmebol said it has initiated disciplinary proceedings against Boca Juniors.
It gave Boca until Saturday to submit the arguments the club deems appropriate, but pundits in Argentina expect the Buenos Aires club will receive an exemplary punishment, including being thrown out of this year's Copa Libertadores.
River Plate were leading their crosstown arch-rivals 1-0 on aggregate after winning the first leg with a goal by Uruguay's Carlos Sanchez.
Separately, a group of Boca Juniors fans has sued the club and its chairman Daniel Angelici for "moral damage" and other unspecified harm suffered by spectators as a result of the incidents at Thursday's clasico.