MEXICO CITY (AP) — As 850 Mexican local, state and federal security personnel prepared to raid a big state prison near the U.S. border, criminals inside orchestrated a wave of chaos outside the walls in Ciudad Juarez.

Ten people were killed in various incidents around the city Tuesday night and early Wednesday as criminals tried unsuccessfully to create a diversion or pressure authorities to stop the raid, officials said.

“At least eight of these murders were tied to the diversion issue,” Chihuahua state prosecutor Jorge Nava said.

Four men who were arrested in the violence said they were paid in methamphetamine to wreak havoc, Nava said at a news conference.

Attackers burned 10 buses, including one transporting assembly plant workers, and five private vehicles. Some of the workers suffered burns trying to escape the bus.

Nava called it a “Machiavellian plan to be able to get authorities to stop the operation.”

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Juarez Mayor Armando Cabada Alvídrez said prisoners likely became aware that a raid was coming because two planeloads of federal police had arrived in Juarez.

The state prison in Juarez is overcrowded, holding more than 3,000 prisoners. It suffers from too few guards, poor hygiene and widespread criminal activity, according to this year’s report from Mexico’s National Human Rights Commission.

On Thursday, Mexican security forces continued working inside the prison, but had not yet reported what they found.

“We go into one of the centers that generates violence to inhibit the violence that’s created in the city from within where they order the murders,” Chihuahua Gov. Javier Corral said. “The intervention was so correct that there was an immediate reaction. They wanted to distract us and wanted to scare us.”

Authorities did not provide details on the killings. But the violence reacting to the government operation was reminiscent of Oct. 17 shootouts in Culiacan that resulted in the release of a son of jailed drug lord Joaquín “El Chapo” Guzmán.

In that case, soldiers had Ovidio Guzmán López on his knees outside a home, but his brother refused to call off attacks around the city that left 13 dead. Security forces eventually let Guzmán go to avoid more bloodshed.

Experts had feared backing down in that situation would become a precedent and spur other groups to use similar tactics.

President Andrés Manuel López Obrador has been adamant in refusing to be drawn into a war against Mexico’s organized crime groups. The number of high-profile shootouts and killings, however, is mounting.