(Bloomberg) -- Police arrested a man who allegedly threw a small explosive at a rally held by Brazil’s presidential front-runner, Luiz Inacio Lula da Silva, in Rio de Janeiro. No injuries were reported.

The man threw an explosive used in Saint John’s Day celebrations, very common in Brazil, into the fenced area that protected the stage where Lula was expected to deliver a speech Thursday night, Rio de Janeiro’s military police said in a Twitter post. He was detained as he tried to escape, they added.

Lula’s office said two small explosives went off at the event, making noise but leaving no one injured. It added that the former president hadn’t yet arrived at the rally. 

The security of presidential candidates is a growing concern among campaign officials as Brazil faces an increasingly polarized race between Lula and President Jair Bolsonaro. On June 15, a drone dropped a foul liquid on supporters of the former president at a rally in the state of Minas Gerais, according to local media.

“We have to strengthen Lula’s security,” Fernando Haddad, who’s running for state governor of Sao Paulo, said in an interview with Bloomberg last month. “It only takes one person to cause a tragedy.”

In 2018, less than a month before the election, then-candidate Jair Bolsonaro was stabbed in a campaign event in Minas Gerais.

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