Brazil's human rights minister said Friday that personnel at a Rio de Janeiro police precinct are the chief suspects in the disappearance of a construction worker who has not been seen since cops picked him up on July 14.

"The investigation should be pursued with the clear and concrete hypothesis that the responsibility lies with the public agents," Maria do Rosario Nunes told reporters in the capital.

Amarildo Souza, 42, disappeared after police at a precinct in the Rio shantytown of Rocinha mistook him for a local drug trafficker and took him in for questioning.

What most concerns the government is that Souza's disappearance followed an encounter with police, Nunes said.

"Police abuse and violence is something we can no longer co-exist with," the human rights minister said, citing the situation in the central state of Goias, where an "immense number" of people have gone missing after being taken into custody by cops.

Hundreds of people turned out on Thursday in Rio de Janeiro and Sao Paulo to demand answers in the Souza case, which prosecutors are treating as a homicide.

The case has also joined the list of grievances raised by participants in nationwide demonstrations that began in June.

Spurred by an increase in transit fares, the protests became increasingly focused on the poor quality of public services, rampant political corruption and the spending of large amounts of taxpayers' money to host high-profile events such as next year's soccer World Cup and the 2016 Olympics. EFE