A homemade bomb has detonated near Bogota's bullring, wounding as many as 26 people. Last month, the first bullfight in four years was held in the Colombian capital.
The improvised device was left in a sewer close to the city's bullring, just a few hours before the last bullfight of the current season was due to take place, officials said.
The explosion shattered windows in nearby apartment buildings, local media reported.
Several police officers, who were maintaining security ahead of the bullfight, were among the 26 people injured. Two of the wounded were reported to be in a serious condition, the city government said on Twitter.
Bogota Mayor Enrique Penalosa denied earlier statements from officials that one policeman had died in the blast.
While some commentators were quick to link the blast to last month's reversal of a bullfighting ban, President Juan Manuel Santos spoke of a deliberate act targeting law enforcement. "We condemn the attacks against police, who guarantee safety in La Macarena," he tweeted.
Another focus of the investigation was the ELN, a left-wing guerrilla group with around 1,500 members that recently started peace negotiations with the Colombian government after five decades of fighting.
Violence after ban u-turn
Bullfighting was made illegal in 2012 by the Bogota's former leftist mayor Gustavo Petro, but the Constitutional Court overturned the ban on January 22, a decision that led to violent confrontations between animal rights campaigners and police.
Last month, police fired tear gas and arrested scores of youth demonstrators to control mobs that physically attacked spectators attending the first bullfight in the capital in four years. Since then, other bullfights have taken place without violence.
But Penalosa all but ruled out that the bullfight protesters were to blame for Sunday's explosion.
"It's not part of our hypothesis," he said after an emergency meeting with his top security aides.
mm/bw (AFP, AP, dpa)