RIO DE JANEIRO (Reuters) - Hundreds of Brazilian soldiers poured into Rio de Janeiro’s Rocinha slum on Friday in a bid to help the cash-strapped state government quell the drug-related violence that authorities blamed for at least four deaths and several injuries there this week.

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The army deployed 950 troops in the sprawling favela, responding to a request from the Rio state government, Defense Minister Raul Jungmann told local television.

In the past week, 60 criminals are believed to have launched an effort to dominate the drug trade in the area, not far from some of the city’s most expensive real estate, and shootings were reported there on Friday morning, according to local media.

The violence in Rocinha is one more sign of the backsliding since the launch of a “pacification” program in 2008 to reduce violence by pushing out drug gangs and setting up permanent outposts in the city’s more than 1,000 favelas.

Police struggled to maintain security gains in favelas in the run-up to the 2016 Olympics in Rio and have continued to lose ground as a fiscal crisis in the city and state lead to cutbacks in spending on police and other essential services.

The military operation in Rocinha on Friday disrupted transportation and businesses in the area, with some schools closing or paring back operations.

“I was going to work and suddenly the police closed off the tunnel in Rocinha and started to patrol with guns. There was a panic at the mouth of the tunnel and I saw people running and heard gunfire,” one witness told Reuters, requesting anonymity.

“I’m still shaking now.”

The outbreak of violence is happening in the midst of the Rock in Rio music festival at the far south end of the city, which has drawn thousands of people with musical acts including Fergie and Aerosmith.

Broadcaster GloboNews on Friday showed relatively calm scenes of matte green military trucks filing down roads into the favela, including soldiers riding on trucks and motorcycles holding assault rifles.

There are up to 10,000 troops in Rio de Janeiro who could be mobilized if needed, the defense ministry said.

“We’re not going to back off in Rocinha,” the governor of Rio state Luiz Fernando Pezao told journalists.