At least 35 people have been detained after demonstrators allegedly set fire to the construction site of an Atlanta public safety training facility that anti-police and environment activists dubbed "Cop City."

A group of "agitators" left the nearby South River Music Festival around 5:30 p.m. and descended on the construction site of the proposed Atlanta Public Safety Training Center "to conduct a coordinated attack on construction equipment and police officers," the Atlanta Police Department said in a statement. 

Authorities noted how the group changed into black clothing and allegedly began to throw commercial-grade fireworks, Molotov cocktails, large rocks and bricks at police officers. 

Though demonstrations at the 85-acre property in DeKalb County secured for a $90 million police and fire training facility have been ongoing, Atlanta Chief of Police Darin Schierbaum said Sunday’s incident marked a "significant escalation" both in the level of violence and the number of individuals involved in the attack.

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cop city fires

Atlanta police released video of fires set to equipment at the construction site of a police and fire training facility dubbed "Cop City." (Atlanta Police Department)

"This wasn’t about a public safety training center. This was about anarchy, and this was about an attempt to destabilize. And we are addressing that quickly," Schierbaum told reporters. "Actions such as this will not be tolerated. You attack law enforcement officers, you damage equipment, you are breaking the law. This was a very violent attack that occurred this evening." 

The FBI and Georgia Bureau of Investigation have joined the probe, he said. 

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"Some of those arrested yesterday were from Massachusetts and New York and France and Canada. So this is a national network, an international group of people that are organized to come to our state to undermine a public safety training center," Georgia Attorney General Chris Carr said in an appearance on Fox News Monday morning. 

Atlanta police said at least 35 people had been detained as of Sunday night. Carr said all but two were from out of state, and 23 individuals were charged with domestic terrorism. 

Schierbaum said Sunday night law enforcement were consulting with both DeKalb County prosecutors and the Georgia Attorney General’s Office.

cop city demonstrators in black

Police say at least 35 "agitators" arrested in attack on "Cop City."  (Atlanta Police Department)

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"I can tell you by just looking at the initial reports, we continue to see a number of individuals not from Atlanta, Georgia, that are present tonight undertaking criminal activities to destabilize the construction of a police fire and training center," Schierbaum said Sunday night. 

"This is not a protest," the chief added. "I made a clear distinction of what a protest looks like. When it is a legitimate protest, you have the full protection of the Atlanta Police Department. This is not a protest. This is criminal activity. And the charges that will be brought forth will show that." 

atlanta police training fires

Atlanta police say demonstrators set fire to equipment and throw explosives at officers.  (Atlanta Police Department)

Before Sunday, at least 19 people had been arrested and charged with domestic terrorism since December in connection to demonstrations at the "Cop City" site. Six of the 19 arrests came out of a violent riot in downtown Atlanta on Jan. 21 that was sparked by the deadly shooting of 26-year-old environmental activist Manuel Esteban Paez Teran by Georgia State Patrol. 

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State patrol had responded to the construction site to clear out demonstrators. Authorities said Teran, who reportedly went by the name Tortuguita and identified as non-binary, shot a trooper in the abdomen before law enforcement officials returned fire and killed Teran.