TAIPEI - A KEY witness who testified against former Taiwan president Chen Shui-bian's wife in a high-profile graft scandal attempted suicide just hours later, officials said on Monday.

Tu Li-ping was found to have taken a massive amount of sleeping pills and attempted to kill herself by ingesting carbon monoxide fumes from her car exhaust outside Taipei late on Friday.

Tu, a Yuanta Securities board director, was questioned on oath and released on bail on Friday in a money laundering probe that has already seen the former president put behind bars.

'She was suspected to use emission gas to poison herself,' a rescuer said, adding that a large quantity of sleeping pills had also been involved.

Tu told prosecutors the former president's wife, Wu Shu-chen, asked her to take 740 million Taiwan dollars (S$34.1 million) in cash to her firm for safe-keeping during a campaign to oust Chen in 2006, Tu's lawyer told reporters.

Tu has admitted giving the Chen family 200 million Taiwan dollars when Yuanta was in the process of merging with another company but denied it was a bribe.

But through her lawyer, the wheelchair-bound former first lady on Saturday denied that she had stashed the 740 million Taiwan dollars and said she only accepted 20 million dollars in the form of a 'political donation' from Yuanta.

Prosecutors have raided three companies, including Yuanta, over their suspected roles in alleged transfers to the Chen family's overseas accounts.

Taiwanese authorities started investigating the former government's financial reforms in August, in particular looking at controversial mergers in the banking sector.

Chen, his wife, son, daughter-in-law, and brother-in-law have all been named as defendants in the money laundering case.

The family agreed last week to return US$21 million (S$32 million) found in their Swiss bank accounts to help the probe, prosecutors said.

Chen, whose pro-independence stance while in office angered Beijing, has repeatedly accused Taiwan's current China-friendly government of being behind the allegations of money laundering, embezzlement, forgery, and taking bribes. -- AFP