Brazilian police are continuing operations in a group of Rio shanty towns where they have been confronting drugs dealers for more than a month.
Wednesday saw the biggest police presence so far
Around 420 officers moved back into an area known as the German Complex a day after staging a big show of strength.
The police action is part of an increasingly assertive security policy in Rio de Janeiro, which has been criticised by some human rights groups.
In Wednesday's action, one person was injured as gun battles broke out.
Brazilian media reported that 300 military police officers and 120 from the national federal police force resumed operations early on Thursday to try to stop drugs and weapons getting into the area.
The confrontation in the German Complex - a group of favelas or shanty towns not far from the international airport in Rio - began more than a month ago after two policemen were killed.
Since then police have maintained a heavy presence in the area and, according to local reports, 64 people have been wounded and at least 17 have died in the past few weeks.
Residents have paid a heavy price in this continuing confrontation, living in constant fear, with schools and shops often closed, the BBC's correspondent in Brazil, Gary Duffy, says.
The confrontation has overshadowed daily life in the area
In the latest shift in strategy, police on Wednesday sealed off access routes into the favelas, searching men, women and children.
The police operation focused on a favela known as Vila Cruzeiro, and involved 250 national force officers and 200 other police officers from across the city.
Throughout Wednesday there were several gun battles and police used heavily reinforced vehicles to maintain their presence.
Rio's governor, Sergio Cabral, who took office earlier this year, has made clear his determination to reclaim parts of the city where drug gangs have taken control.
But human rights groups have criticised the tactics and say killings by police are not properly investigated.