SAO PAULO -- Brazilian authorities on Thursday began investigations into allegations that security personnel beat members of a visiting Argentine football club at the halftime of the Copa Sudamericana.
South American football officials described it as the most serious incident in decades in the country that will host the 2014 World Cup -- raising fears about Brazil's ability to secure the event and putting a blemish on the country's reputation just months before the Confederations Cup.
Wednesday's final was called off and Sao Paulo was awarded the title when Argentina's Tigre refused to take the field for the second half of the second leg of the final. Sao Paulo was leading 2-0, with the first leg having ended scoreless.
Officials of the Argentine club said their players and staff were beaten by security officials in the dressing room area at halftime and guns were drawn. Brazilian authorities denied, however, that any weapons were brandished by the private security guards.
The trouble off the pitch followed sharp scuffles between the teams at the end of the first half.
The Sao Paulo State Public Safety Department said it would interview witnesses, players and security personnel, while South American football's governing body CONMEBOL said it would also conduct a "thorough investigation" into the incident.
CONMEBOL spokesman Nestor Benitez told The Associated Press that what happened in Sao Paulo "stains the good image of South American football." He said it was the most serious incident of its kind in 25 years.
Despite that, there was little debate within Brazil itself over the match -- many of the comments posted on Twitter and other social networking sites hurled insults at the Argentine team for being poor sports, accusing them of wanting to fight more than play once they went down by two goals.
Violence is common around Brazilian football -- images of police batting at rowdy fans is common, and fan-on-fan violence has begun to creep up again after a quiet few years. However, security personnel getting into a fight with players as is being alleged was virtually unheard of.
Shortly after arriving back home, Tigre captain Martin Galmarini described the violence as a "dramatic, chaotic and hellish episode."
He said the team was harassed as it arrived at Sao Paul's Morumbi stadium -- a common occurrence in South American football.
"They broke all the windows of the van, hurled rocks and beer bottles and we are not allowed to warm up on the pitch," he said.
The trouble at Morumbi stemmed from confrontations between the teams following a first half in which the hosts had taken a 2-0 lead after goals from Lucas and Osvaldo.
It was unclear what happened in the dressing room area, but Argentine and Brazilian television showed what appeared to be blood-spattered walls. Argentine television also showed several Tigre staff members with bruises and bloody faces. Brazilian television showed security personnel that were also bruised and battered.
"Police entered and struck our players with clubs," Gorosito told Argentine television. "It was crazy. What happened was crazy."
A Brazilian police officer who identified himself as Major Gonzaga told reporters that police were called to break up a fight between Argentine players and Sao Paulo security guards, but that that no one was armed and that police did not act violently.
Joao Paulo de Jesus Lopes, one of Sao Paulo's vice presidents, told reporters that Tigre players tried to "break into the Brazilian team's locker room and injured some of Sao Paulo's security guards.
"We were fighting for 15 minutes with people trained by, and wearing the colors of Sao Paulo. There was no need to do something like this. They were winning the match," said Tigre keeper Albil.
Romer Osuna, a Bolivian official with CONMEBOL, said Tigre players were afraid to return to the field after the first half of play.
"The Tigre people declined to play because they considered security was not good enough," Osuna told Fox Sports.
Referee Enrique Osses of Chile awarded the victory to Sao Paulo after waiting about 30 minutes for Tigre to retake the field.
Sao Paulo scored twice in five minutes in the first half -- a left-footed drive from Lucas in the 23rd and a lobbed shot from the right wing by Osvaldo in the 28th.
Sao Paulo, one of Brazil's most famous clubs, is a three-time winner of the Copa Libertadores, South America's most prestigious club tournament. It has also won the Club World Cup once, and twice won the Intercontinental Cup.
This was the club's first Copa Sudamericana title.
Tigre was playing in its first international final and has never won the Argentine first-division title.
Information from The Associated Press was used in this report.