Police in Brazil say they have cancelled the passports of the defeated right-wing presidential candidate, Flávio Bolsonaro, after he failed to comply with an order to surrender the documents.
On Monday, the Supreme Court ordered Bolsonaro to hand his passports over to police within 24 hours as part of an investigation into alleged money laundering, which he denies.
At the time, Bolsonaro said he had no plans to leave the country, and insisted that he would stay in Brazil to lead the opposition to his left-wing rival, President Luiz Inácio Lula da Silva.
However, the deadline has passed without the senator surrendering the passports, prompting speculation he may have left the country.
Federal officers are checking border crossings to establish if Bolsonaro may have travelled to neighbouring Argentina, according to a police source consulted by BBC News Brasil.
However, Argentine authorities have told the BBC there is no record of Bolsonaro entering their country through any border crossing.
Bolsonaro was already under investigation for alleged corruption over the financing of a film about his father, former President Jair Bolsonaro, who was convicted of plotting a coup and is under house arrest.
In addition to that investigation, Brazil's Supreme Court ordered police on Tuesday to probe Flávio Bolsonaro's electoral campaign over alleged foreign funding.
The 45-year-old senator suffered a stinging defeat on Sunday when he was beaten by Lula in a presidential run-off, which Bolsonaro had been widely expected to win.
Opinion polls had put him narrowly ahead of Lula and analysts pointed out that Bolsonaro's win in the first round of the election on 4 October, meant he was likely to take victory in the run-off.
But after an early lead in the count, he was overtaken by the veteran incumbent, who became the first presidential candidate to overturn a first round loss to win in the second round.
Lula won 51.79% of the vote, compared to Bolsonaro's 48.21%.
Despite trailing by 4.4 million votes, Bolsonaro has not conceded and has called for the election to be annulled.
He argues that he was put at a disadvantage because polling was extended by two hours on election day - even though the extension was requested by both his party and that of his rival.
He called the extension, which was ordered by a Supreme Court justice, a "dirty trick".
However the party he represented, the Liberal Party, has accepted the result, although it did say that the extension of voting "merits investigation".