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Twelve people suspected of discussing plans to attack the Rio Olympics, including a "biochemical attack" on a water reservoir, were indicted in Brazil Friday, a source close to the investigation told NBC News.

The men were arrested in a series of anti-terrorism raids in late July, a couple of weeks before the Olympic Games. The group pledged allegiance to an ISIS offshoot, authorities said.

Brazil’s Justice Minister at the time called the poorly organized group “absolutely amateur” with “no preparation at all." The source said the plot was more serious than initially described.

Security officers patrol outside the Sambodromo during the Rio 2016 Summer Olympics on Aug. 14. SERGIO MORAES / Reuters, file

The men allegedly discussed a plan to contaminate one of Rio de Janeiro’s water reservoirs to attack the Games, according to court documents reviewed by NBC News.

It doesn’t appear any of the members of the group knew each other aside from conversations online and messaging apps, according to the documents.

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One suspect, posting under the alias Alisson Mussab, allegedly said on Telegram: "Have you imagined a biochemical attack, contaminating the water of a water station?"

Related: Facebook, Twitter Cooperated With Brazil in Probe of Alleged Militants

The documents don’t indicate any chemicals, weapons, or bomb-making materials were found, but members of the group allegedly distributed recipe for gunpowder and instructions to make homemade bombs, according to court papers.

They are accused of "preparing terrorist acts with the purpose of realizing the offense" and other offenses.

The suspects, all Brazilian citizens, had declared loyalty to the terror group ISIS and discussed plans in email threads, and via messaging apps like Telegram and WhatsApp, according to court documents.

Some celebrated other terrorist attacks, like the shooting at the Orlando nightclub. "I liked the attack,” wrote another suspect about the Orlando massacre — using a laughing emoji and celebrating the number of dead and wounded, according to court documents.

The raids were part of an ongoing operation dubbed "Operation Hashtag," the first police operation of its kind in Brazil’s history that led to the arrest of a total 15 alleged suspected ISIS sympathizers across 10 states.

The suspects, who are believed to part of the Jundallah group, which translates to Soldiers of God, a group affiliated with ISIS, were arrested between the months of June and August in three separate phases. Brazilian authorities, with the help of the FBI, had been monitoring these groups since May.

These arrests were the first made under Brazil’s new anti-terrorism law approved in March by recently impeached president Dilma Rousseff.

Before, the crime of terrorism was not clearly defined in Brazil and was treated as any other common crime; now an individual can face up to 22 years in jail if found guilty of preparing terrorist acts.

If the chemical attack could be carried out, the suspects also allegedly discussed carrying out an attack similar to the one carried out at the Boston Marathon in 2013, which killed 3 and wounded 264 others.

According to the source, all 12 suspects will be charged in the next few months with crimes ranging from preparing terrorists acts to integrating a terrorist organization. Those two charges combined carry up to 30 years in federal prison.