Image copyright AFP Image caption Bolsonaro made the claim last week on Twitter
Brazil’s Supreme Court has launched an investigation into incendiary allegations made by far-right presidential candidate Jair Bolsonaro.
Mr Bolsonaro, a senator from Rio de Janeiro, is accused of spreading false information about the increase in measles deaths and attacks in Buenos Aires.
In tweets last week, he said some 100 people had been killed by measles vaccination campaigns in Brazil.
The Supreme Court says it needs evidence to determine if Mr Bolsonaro broke the law.
A Senate judge who opened the probe will seek the records of the public prosecutor’s office and the health ministry to establish if the claims are true.
Image copyright AFP Image caption Brazil’s Health Ministry have denied the claims on their Twitter account
Last year, more than 60 million children were vaccinated against measles in Brazil, according to a study cited by Mr Bolsonaro’s press office.
It says the vaccines were not being provided to children in poorer areas, which is where the attacks in Argentina have been blamed.
Presidential candidate Fernando Haddad of the ruling Workers’ Party says Mr Bolsonaro is using the incident to destabilise the government and the people of Brazil.
What do the leaders of Latin America’s largest country say?
In Uruguay, which also has a large indigenous population, President Tabare Vazquez said Mr Bolsonaro’s comments showed he could not be trusted.
“What would the UN think? The Latin American common will never sit silent over such persecution of those suffering from the scourge of this disease,” he told reporters.
Elected as an independent, Mr Bolsonaro has spoken passionately about guns, criminality and crime.
He has released a programme which would give police and the military more powers to crack down on drug gangs.