One person died of a "cardiorespiratory arrest" on Thursday following violent clashes that started outside a football match involving Gimnasia and Boca Juniors on the outskirts of the capital before spilling into the stadium and onto the pitch, authorities said.
Police fired rubber bullets and tear gas as they attempted to stop fans attending the match between top-flight teams Boca Juniors and Gimnasia y Esgrima La Plata from pushing into the already crowded venue. More than 100 people were injured in chaotic scenes.
"I confirm that there is one person dead. This person died of cardiorespiratory arrest," said Buenos Aires Province Security Minister Sergio Berni.
The unrest outside the Juan Carmelo Zerillo stadium in La Plata, about 50 kilometres (31 miles) south of Buenos Aires, continued inside, where shocked spectators were seen squeezing through fencing to escape the violence and get onto the field.
"There were about 10,000 people around the stadium trying to get in, some with tickets, some without. Everyone could see that the stadium was very full," claimed Eduardo Aparicio, head of a government agency tasked with preventing violence in sports.
"All this is being investigated," including "the actions of the police," he added.
Authorities at San Martín hospital in La Plata confirmed the death of 57-year-old César Regueiro from cardiac arrest as he was being transferred from the stadium to a hospital.
A cameraman for sports channel TyC was injured by rubber bullets while dozens of spectators were suffering from the effects of tear gas and had been taken to hospitals, according to local media.
'The air became unbreathable'
The game was suspended after nine minutes due to a lack of security, referee Hernán Mastrángelo said.
"It affected all of us on the field," he added. "The air became unbreathable. The situation got out of control and there were no security guarantees."
Explosions were heard inside the stadium and smoke from the fumes quickly reached the pitch.
The players, the referee and technical staff members were forced to evacuate the field.
At the same time, fans, including children being led or carried by adults, rushed from the stands and onto the pitch, where people were seen sitting or lying down apparently recovering from tear gas exposure.
"The first thing I saw was that people had started to flee the stalls and I began to feel the effects of the gas. I thought about my family and I started to worry," Nicolás Contín, a Gimnasia player, said from the changing room where he had carried his young son. "I'm angry about everything that happened."
The match came at a critical point in Argentina's Primera Division, with Gimnasia trying to stay in the title race and Boca looking to move into first place.
"What was going to be a party ends in this. It hurts us all what happened, it is tremendous and we regret it," Boca Juniors manager Hugo Ibarra told reporters.
The Argentine Football Association (AFA) issued a statement in which it "strongly repudiated the publicly known events that took place today in the vicinity of the Gimnasia y Esgrima La Plata stadium" and expressed "its commitment to continue working to eradicate this kind of episodes that tarnish the celebration of football."
Clashes inside and outside Argentina's stadiums have resulted in more than 300 deaths since soccer became professional in the 1930s, with two-thirds of the deaths occurring after the 1990s, according to local NGO Salvemos el Fùtbol.
The violence in La Plata comes just five days after one of the deadliest disasters in soccer history in which 131 people were killed in a stadium crush in Indonesia.
The incident in the city of Malang also descended into tragedy after police fired tear gas into packed stands.