A member of his official military detail has been arrested on route to this week’s G20 summit in Japan – after being found with some 39kg of cocaine.
The Brazilian Air Force officer was detained during a stopover in Seville, Spain.
“The serviceman was found to have cocaine in his hand baggage that weighed a total of 39kg,” a spokesperson for the Guardia Civil said. “He was arrested on suspicion of drug trafficking and is currently in custody at our Seville headquarters waiting to appear before a judge.”
He was later named as 38-year-old Sergeant Silva Rodrigues by the Brazilian TV network RecordTV.
The plane – an advance flight ahead of Mr Bolsonaro’s own journey – was carrying a military delegation tasked with protecting the president during the summit in Tokyo.
Mr Bolsonaro confirmed the arrests in a statement on Tuesday, saying he had been informed of the incident by the country’s defence minister.
He said: “I immediately ordered the defence minister to cooperate with Spanish police to establish the facts and cooperate with every stage of the investigation, and to launch an investigation by the military police.
“There are around 300,000 men and women in the armed forces who are trained to uphold the highest principles of ethics and morality.
“If the airman is found to have committed a crime, he will be tried and convicted according to the law.”
Speaking to reporters in Brasilia on Wednesday, vice-president Hamilton Mourao appeared to assume the officer’s guilt.
“It's obvious that, given the amount of drugs he had on him, that he didn't just buy them around the corner and take them with him,” he said. “He was working as a qualified drug mule, let's put it that way."
Right-winger Mr Bolsonaro came to power in January on a promise to crack down on widespread crime in the South American country – including targeting the drugs trade.
Just this month, he passed new legislation which will toughen penalties for traffickers and require users to undergo rehabilitation or face prison.
More about: Brazil