Brasilia, January 14 (RHC)-- Twelve people have been killed in Brazil’s Campinas after violence erupted in the southeastern city.

Security sources said that a 20-member group of attackers, armed with sticks and stones, went through a bus terminal in Campinas where five of the overnight deaths happened.

Police said they torched three buses and looted seven others. In addition, armed criminals riding in vehicles murdered the other victims, including an off-duty policeman.

"We have not established whether these deaths are related. All we know for now is that they occurred in the same area of Campinas," the spokesman stated.

A spokesman said police were investigating a number of possible motives, "including revenge, conflicts between rival gangs or even police executions."

According to reports, police have detained nobody so far in the city located 90 kilometers (55 miles) from the state capital, Sao Paulo.