Backed by dozens of armored vehicles and a helicopter, nearly 1,000 police officers, agents and troops invaded the downtown slums and easily took control without any exchange of gunshots in less than two hours.
Police spokesman Henrique de Lima Castro Saraiva said authorities will now begin installing police units in the shantytowns under a program in which security forces have been taking over and pacifiying the city's poor communities.
Authorities said that while police searched for drug traffickers, weapons and drugs, they found a German man who is living illegally in Brazil and apparently helped treat injured gang members at a house in a slum.
Police Col. Aristeu Leonardo told Globo TV that the man was wearing a doctor's jacket when he was detained. He said the man confessed he had acted as a doctor even though he never finished his medical studies in Germany.
Leonardo said the man, who was not immediately identified, was only a paramedic whose tourist visa expired in 2007.
"He was not supposed to be working because he is not a doctor and because he supposedly was a tourist," Leonardo said. "Now we will investigate whether the place he was working was used to treat drug traffickers or if he only provided medical services to the community. Either way, it was illegal."
Brazil's federal police department planned to investigate the alleged irregularities on the man's visa.
The Associated Press was not able to immediately contact him.
Police found several first-aid kits and medical equipment to conduct surgeries at the house where the German was found in the Mineirinha shantytown. A notebook with a list of unidentified patients and the medical procedures done on them also was seized.