(São Paulo) - São Paulo authorities should conduct a prompt, thorough and impartial investigation into allegations that police planted evidence of criminal activity on two protesters who were arrested on June 23, 2014, Human Rights Watch said today.

“Protesters who engage in vandalism and violence should be held accountable,” said Maria Laura Canineu, Brazil director at Human Rights Watch. “But so too should any police who plant evidence and deliberately accuse protesters of crimes they know that they didn’t commit.”

On June 23, civil police officers arrested Fábio Hideki Harano, 26, and Rafael Marques Lusvarghi, 29, during a largely peaceful protest in São Paulo. Police claimed that they found a homemade explosive device in Harano’s backpack and a “bottle of yogurt that smelled heavily of gas” on Lusvarghi. Both were arrested for possessing illegal weapons, resisting arrest, conspiring to commit crimes, “inciting crime,” and “disobeying police authority.”

However, Harano’s lawyer told the media that there were no weapons in his backpack, which is consistent with an account given to Human Rights Watch by Father Julio Lancellotti, a well-known human rights advocate who was present at the time of the arrest. “I was entering the subway station when I saw two civil police officers approaching Harano and opening his backpack,” Father Lancellotti told Human Rights Watch. “They took out a gas mask and crackers, but no explosive devices.”

Human Rights Watch also reviewed video footage of the police searching the backpack, which appeared to confirm the accounts by the priest and Harano’s lawyer.

Harano and Lusvarghi are being held at the Tremembé prison and 8th civil police station jail, respectively, under preventative detention powers, although neither has been formally charged. The police report about the arrests, reviewed by Human Rights Watch, states that police decided to search Harano after seeing him “lead a group that was about to begin to destroy property.” Lusvarghi was followed because he “maintained a close dialogue with Harano,” the police report says.

On June 26, a judge authorized Harano’s and Lusvarghi’s continued detention on the basis that “while they are both first offenders, releasing them would threaten the public order.” However, the São Paulo Public Defender’s Office told Human Rights Watch that the judge simply rubber-stamped the police version of events, ignoring testimony and other evidence in favor of the detainees. Neither Harano nor Lusvarghi was actually brought before the judge in order to have their detention authorized. Public defenders filed an habeas corpus petition yesterday with the Superior Justice Tribunal to release Harano and Lusvarghi. The men must be criminally charged or released within 15 days of their arrest.

“Governments have a duty to stop violent attacks on police, public and private property,” Canineu said. “But unless São Paulo authorities can provide credible evidence that Harano and Lusvarghi committed crimes, the two men should be granted immediate and unconditional freedom.”