Brazil's Supreme Court has agreed to include right-wing former president Jair Bolsonaro in its investigation into the storming of government buildings in Brasília.
It is the first time that Bolsonaro has been named among those potentially responsible for the 8 January riots.
It comes days after Bolsonaro posted a video questioning the legitimacy of October's presidential election.
Prosecutors said Bolsonaro may have incited a crime by making such claims.
They asked the Supreme Court on Friday to include the ex-president in the investigation.
The Bolsonaro video claimed that President Luiz Inácio Lula da Silva was not voted into office but rather chosen by the Supreme Court and Brazil's electoral authority.
While the video was posted after Sunday's riot and later deleted, the prosecutor general's office argued its content was sufficient to justify investigating Bolsonaro's conduct beforehand.
Thousands of radical Bolsonaro supporters, who continue to claim that the election was rigged, stormed the country's Supreme Court, Congress and presidential palace on Sunday.
They had been camping in and around the capital Brasilia for weeks calling for a military coup.
Meanwhile, Bolsonaro has been admitted to a hospital in Florida with abdominal pain, his wife said.
He left Brazil for the United States in late December, after refusing to take part in the handover of power to Lula.
Many businessmen and officials are being investigated, including Brasilia's former head of security, Anderson Torres, who flew to the US ahead of the riots.
On Thursday, police visited his home and found a document reportedly trying to reverse the election result.
Torres argues the document has been taken out of context, but Justice Minister Flavio Dino has said he must turn himself in by Monday or face extradition.
Earlier, Lula accused Bolsonaro's allies of aiding an attack on the presidential palace on Sunday.
More than 1200 people have been formally arrested and are being charged in relation to the riot at Brazil's Congress.
Arrest warrants have already been issued for several top officials accused of being "responsible for acts and omissions" that led to the riots.
- BBC