Rana Koleilat is wanted in Lebanon on fraud, embezzlement and forgery charges related to the collapse of Bank al-Madina in 2003 and was arrested in Brazil on Sunday.
In a Sao Paulo jail on Wednesday, the fugitive banker cut her left wrist with a blade from a contraband eyeliner sharpener, but police denied she tried to commit suicide, saying it was only an attempt to draw attention to her plight.
UN investigators have told police they want to question Koleilat in connection with the February 2005 assassination.
Brazilian police said the investigators want to know whether money allegedly diverted from Al-Madina Bank in Lebanon, where Koleilat worked, was used to finance the killing.
Koleilat spent a few months in prison in Lebanon last year, but then jumped bail on fraud charges in a banking scandal and fled the country, allegedly with Syrian help.
She was arrested on Sunday by Brazilian police at a hotel apartment on the outskirts of Sao Paolo, Brazil's largest city with a sizable community of Lebanese descent.
Al-Hariri was killed on 14 February in a truck bombing of his motorcade on a Beirut street, a turning point that sparked mass anti-Syrian protests and intensified international pressure that forced Syria to withdraw its army from Lebanon.
The UN commission in two earlier reports blamed Syrian and allied Lebanese intelligence officials in the murder of al-Hariri and 20 others.
Al-Hariri (R) was assassinated
on 14 February 2005
Speculation that Koleilat, 39, had fled to Brazil had been circulating in Beirut in recent months.
So why was she arrested on Sunday?
The Brazilian authorities said they acted on an anonymous tip.
However, Koleilat's arrest came before the chief UN investigator briefs the Security Council Thursday on the investigation's progress, and her arrest could provide more ammunition against Syrian officials implicated in the assassination, particularly the last Syrian intelligence chief in Lebanon.
Lebanon has no extradition treaty with Brazil, where Koleilat also faces charges of attempting to bribe police officers to release her.
Koleilat's Brazilian lawyer said she told him she knows nothing about Al-Hariri's assassination or the bank's missing money and that she offered no bribe.
Koleilat's connection with the private bank was engulfed in controversy.
During her 12 years there, she rose from a clerk to an executive making top decisions.
Koleilat quickly became the centre of the scandal shortly after it broke at Al-Madina in July 2003.
After detecting a cash deficit of more than $300 million, along with other irregularities, the Central Bank stepped in and took control of Al-Madina.
A suit by the owners of the bank accused Koleilat of issuing a bad check for $3 million and of forging bank documents with the aim of embezzling.
Several depositors also have filed suits against her and the bank owners.
Koleilat was interrogated and jailed several months in 2004.
Lebanon's Central Bank stepped
in to take control of Al-Madina
She became an instant celebrity at the height of the banking scandal in 2003, with the media scrutinising her lifestyle, gifts and purchases.
It is alleged that her power stems from secretly marrying one of two brothers owning the private bank and that she had paid protection money to Syrian intelligence officials.
Her case highlights the political corruption that ravaged Lebanon for decades, fuelled by the dominance of Syria.
Paying off Syrian intelligence officers and giving gifts to influential politicians and business people for protection and favour was common practice during the period when Syria, through its intelligence network, influenced everything in Lebanon, from picking a president to harassing a political foe, and even cutting a business deal or finding a stolen car.
Koleilat was freed on bail less than two months before al-Hariri was killed, allegedly under pressure from Major General Rustum Ghazale, Syria's intelligence chief in Lebanon.
Koleilat was whisked out of the country through Syria before the collapse of Syria's power in Lebanon with the withdrawal of its army in April.
She reportedly spent a few months in Cairo, Egypt, before travelling to Brazil.
Barely a month later, the bank's fugitive chairman, Adnan Abu Ayash, filed a lawsuit through a lawyer accusing Koleilat, Ghazale and three of his brothers of laundering and theft of more than $70 million in depositors' money.
Lawyer Jean Azzi claimed Koleilat used to withdraw money from the bank and transfer it to accounts she opened in the names of Ghazale and his brothers.