ATLANTA (AP) — Police used tear gas and flash-bang grenades Monday to halt a march seeking to stop construction of a police and firefighter training center in Atlanta.

More than 500 people on Monday marched about 2 miles (3.2 kilometers) from a park to the site, which is just outside the Atlanta city limits in suburban DeKalb County.

A wedge of marchers, including some in masks, goggles and chemical suits intended to protect against tear gas, pushed into a line of officers in riot gear on a road outside the training center site. Officers pushed back and then responded with tear gas, with one protester throwing a canister back at officers.

Protests against the proposed training center — dubbed “Cop City” by opponents — have been going on for more than two years. Georgia Attorney General Chris Carr obtained a sweeping indictment in August, using the state’s anti-racketeering law to target 61 protesters, characterizing them as “militant anarchists.”

Some marchers on Monday retreated from the clash while others tried to cleanse themselves of the effects of the tear gas. Dozens of protesters ran into the woods on the property where the training center is being built, but then joined hands and exited the property. They and other marchers then retreated, with no apparent arrests. Vomiting and irritation from the tear gas were the only apparent injuries.

Police agencies including the DeKalb County police department and Georgia state troopers were guarding the site, including armored vehicles.

Protesters called the event “Block Cop City” and had held events across the country seeking support for Monday’s demonstration. It was the latest effort to stop construction in a protest effort that has galvanized environmentalists and anti-police protesters across the country. Protester Sam Beard, rallying the crowd Monday said the movement has fused environmentalists and police abolitionists and is a model of resistance against police militarization.

Atlanta Mayor Andre Dickens and other supporters say the 85-acre, $90 million facility would replace inadequate training facilities, and would help address difficulties in hiring and retaining police officers. Opponents have expressed concern that it could lead to greater police militarization and that its construction in the South River Forest will worsen environmental damage in a poor, majority-Black area.

Some protesters in Monday’s march hoped to reoccupy the wooded area that includes the construction site and adjoining park. Activists spent months camping in the woods until police pushed them out in January. That sweep included the fatal shooting in January of 26-year-old protester Manuel Esteban Paez Terán, known as Tortuguita. A prosecutor last month said he would not pursue charges against the state troopers who shot Paez Terán, saying he found that their use of deadly force was “objectively reasonable.”

Paez Terán’s parents were among speakers Monday before the march.

Protests against the project, which have at times resulted in violence and vandalism, escalated after that. Prosecutors now characterize it as a conspiracy that includes a wide variety of underlying crimes that range from possessing fire accelerant and throwing Molotov cocktails at police officers to being reimbursed for glue and food for activists who spent months camping in the woods near the construction site.

Most of those indicted in August had already been charged over their alleged involvement in the movement. RICO charges carry a sentence of five to 20 years in prison that can be added on top of the penalty for the underlying acts.

Among the defendants: more than three dozen people who were previously facing domestic terrorism charges in connection to the protests; three leaders of a bail fund previously accused of money laundering; and three activists previously charged with felony intimidation after authorities said they distributed flyers calling a state trooper a “murderer” for his involvement in Paez Terán’s death.