Brazil has suspended a clinical trial of China's coronavirus vaccine, citing a severe adverse incident.
The country's health regulator, Anvisa, said on Monday (November 9) the event took place on October the 29th, but did not give anymore details.
While Sao Paulo's medical research centre Butantan, which is leading the trial, was surprised by the move.
Its head said the decision was related to a death but added that it was not connected to the vaccine.
Sinovac did not immediately respond to requests for comment.
President Jair Bolsanaro has previously criticised China's vaccine as lacking credibility.
Comments which put him in direct opposition to the governor of Sao Paulo, Joao Doria, who has spearheaded the project.
Doria, who's widely expected to run against Bolsonaro at the next presidential election in 2022, plans to import and produce the vaccine, which could be rolled out as early as January.
He's already started building a facility which will have the capacity to produce 100 million vaccines a year. And an order for 120-thousand doses of Sinovac is already due to arrive in a little over a week.
Trials of the vaccine are also being carried out in Turkey and Indonesia, neither country has reported problems. And thousands of people in China have already received doses under an emergency use program.
Brazil has been one of the countries worst affected by the coronavirus, recording more than 5.6m cases and more than 160,000 deaths.