efe-epaLa Paz

The death toll from an explosion that marred Carnival festivities in the southwestern Bolivian city of Oruro stands at four and evidence of a bomb has been found at the scene, officials said Wednesday.

Two of those killed in the blast Tuesday evening were minors, national police commander Faustino Mendoza told reporters.

A police forensics team discovered a crushed plastic container with an aluminum fragment and the remains of a detonator capable of activating "more than 3 kg (6.6 lbs.) of dynamite," he said.

Nine other people hurt in the explosion remained hospitalized on Wednesday.

Three suspects are in custody, Defense Minister Javier Zavaleta said in comments to Red Bolivision TV, though adding that it was too soon to say whether they were behind the explosion.

"We are not ruling out any hypothesis," the minister said of the blast, which happened near the spot where another explosion last Saturday left eight people dead and 40 wounded.

Police initially attributed Saturday's explosion to a gas leak, but authorities are taking a fresh look at that incident, Zavaleta said.

He went on to cite the appearance on social media shortly after Tuesday's explosion of apparently faked audio recordings purporting to document the blast as leading the government to suspect a larger "operation."

"We don't rule out that (Tuesday's explosion) could have been coordinated with Saturday's, but it's being investigated," Zavaleta said.

The minister said that officials have no reason to expect further explosions in Oruro, a city of roughly 285,000 people.

The governor of Oruro province, Victor Hugo Vasquez, was quick to label Tuesday's blast a "criminal act."