MANAUS, Brazil (AP) — Brazilian security officials said Tuesday nine inmates blamed for killing sprees in several prisons will be transferred to stricter federal facilities, after two days of unrest left 55 prisoners dead and authorities rushing to prevent the violence from spreading.

Fighting between inmates began around noon on Sunday in a prison complex in Manaus, the capital of the northern Amazonas state. The state prison secretary said the deaths were the result of infighting in one of the prison's criminal groups.

"The dead individuals are members of this group, involved with drug trafficking," he said in a statement, without specifying which fraction.

In the Manaus complex, an emergency security protocol was activated and within 45 minutes the situation was under control, local authorities said. Still, 15 inmates were killed, either asphyxiated or murdered with hand-crafted arms such as sharpened toothbrushes.

The following day, more fights erupted in three other facilities, all in the same city of Manaus, leaving another 40 inmates dead and pushing federal authorities to send a special taskforce to avoid a scenario similar to that of January 2017, when weeks of gruesome prison killings left over 120 victims.

The nine inmates who will be transferred to federal facilities on Tuesday are believed to have ordered the killings, authorities said. As a precautionary measure, another 200 prisoners have also been moved to different cells.

While police forces were intervening to separate inmates considered at-risk, two detainees were shot as they tried to take prison staff hostage.

"As the troop advanced, they (inmates) were killing people choking them inside their cells," said Col. Vinicius Almeida, who leads the state prison office.

In the meantime, family members of inmates gathered outside the prisons, waiting for information on their loved ones. Some outside the Puraquequara Prison Unit (UPP) on Tuesday told The Associated Press they had heard people screaming and calling for help from within the facility Monday night.

"I'm going to stand here until they give me some news," said Ediane Costa Soares, 38, whose 19-year-old son Anderson Soares de Souza, is an inmate at UPP.

Her son does not appear on the list of victims, but Costa Soares wants reassurance about her son's well-being after the riots. "They have not told us anything."

The Anisio Jobim Prison Complex, where 15 inmates died Sunday, was the scene of gruesome infighting two years ago that left 56 prisoners dead. Many of those victims had their heads cut off or their hearts and intestines ripped out.

Drug-trafficking and other criminal gangs run much of their day-to-day business from Brazil's prisons, where they often have wide sway. The 2017 slayings were largely gang-related, prompting authorities to increase efforts to separate factions and frequently transfer prisoners.

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AP video journalist Caivano reported from Manaus. AP journalist Jeantet reported from Rio de Janeiro.