Authorities have blamed a criminal gang of eight men for shooting attacks that killed five people and wounded more than 20 riding on two buses carrying supporters of Nicaragua's governing party last month.
The national police director, Aminta Granera, yesterday said the motive appeared to be criminal rather than political.
He said the gang planned the attack weeks before shooting at the buses on July 19, the anniversary of the revolt that swept the Sandinista movement into power.
"I don't think there necessarily has to be a theft involved to make it a criminal case," he said at a news conference. "There are no armed groups with political motivations."
Granera said one of the suspects has links to Mexico's Zetas drug cartel. He identified that suspect as a migrant trafficker named Jose Ricardo Cortes.
Cortes and all but one of the seven other suspects have been arrested. They face charges of homicide, organized crime, conspiracy and weapons possession.
Prosecutors had earlier arrested a bus driver hired to transport the Sandinista movement supporters, saying he was suspected of helping plan the attacks on a highway. The bus driver has denied any involvement.
In addition, three other men were previously accused of throwing rocks at the buses as a way to slow them down, making them easier targets for the shootings.
There has been a long history of violence between rival political groups in Nicaragua, often involving Sandinista groups attacking opposition protests.
