(CNN) -- Soldiers and police will remain in the Alemao favela complex in northern Rio de Janeiro, Brazil, until a more permanent policing solution can be put in place, the local governor said Monday, according to the official Agencia Brasil.
His announcement came just one day after authorities launched a massive sweep of the favela, or slum.
"We will not rest on the laurels of yesterday's victory. We wake up early with the next challenges, which are to effectively regain the territories still occupied by the parallel power," said Sergio Cabral, governor of the state of Rio de Janeiro, according to Agencia Brasil.
Military police told reporters they were entering the virtually impenetrable labyrinth of slums, searching for drug gang leaders and illegal drugs.
CNN affiliate TV Record showed images of armored vehicles entering the slum Sunday morning, followed closely by police trucks and helicopters equipped with military rifles.
Brazil, which will host the World Cup in 2014 and the 2016 Olympics, is under increasing pressure to crack down on violent crime and clean up its slums.
On Saturday, police spokesman Mario Sergio Duarte declared an ultimatum against drug gangs in the complex, stating that a military attack was imminent.
"We will not retreat in our decision to bring peace to Rio," Duarte said. "We are in our final stages of reaching the traffickers in the Alemao complex."
Police had offered drug gang leaders the chance to surrender, but they refused, Brazilian military police Col. Lima Castro said in an interview with CNN affiliate Band News Sunday.
At least 37 people have died, 123 have been arrested and 130 have been detained since last Monday, police said. Four policemen have been hurt.
Journalist Luciani Gomes contributed to this report.