The Special Investigation Unit (SIU) did not disclose much about the raid at Chen's home, in an upscale apartment building at Taipei's Xinyi District.

"We came to Chen's residence...to investigate the (alleged money laundering) case this morning...The former president and his wife explained transactions of the money," said Chu Chao-liang, a spokesman for the SIU.

Chu said prosecutors did not use warrants, as the couple were cooperative.

Prosecutors in Tainan also searched the home of the former first lady's brother, Wu Ching-mao, in the afternoon.

Chen has claimed that his wife Wu Shu-chen had remitted US$20 million out of Taiwan in January 2008 without letting him know. He said the money was from campaign funds that he had failed to declare.

But prosecutors are trying to determine whether the couple was trying to launder illegally obtained money.

Meanwhile, Taiwan's top prosecutor has ordered a probe into a seven-month delay by the Ministry of Justice Investigation Bureau (MJIB) in reporting information it had received about former Chen's alleged money laundering.

State Public Prosecutor General Chen Tsung-ming said the SIU under his office did not realize that the MJIB had been long aware of the former president's alleged money laundering until recent exposure of the case in the media.

The prosecutor general said he already instructed the anti-corruption task force to look into the MJIB's delay in reporting Chen's case to his office.

Media reports have disclosed that the MJIB already had been informed by the Cayman Islands in January of this year about alleged money laundering, involving the ex-president's son, Chen Chih-chung, and daughter-in-law, Huang Jui-ching.

An SIU ad hoc team that has already been investigating the former first couple over their alleged embezzlement of the presidential state affairs funds said it first learned about the overseas money laundering from the press.

They said they then contacted the MJIB, which admitted that it already had obtained information from the Cayman Islands in January.

The ad hoc team said the SIU did not get full details of the case until Aug. 14, when prosecutors handling related cases got together in a meeting.

But by then, the former president's son and daughter-in-law had already left Taiwan, on Aug. 9, it said.

The MJIB confirmed that it had received information concerning the alleged money laundering case in January.

The bureau claimed the information was then passed onto then MJIB Director Yeh Sheng-mao, whom was then expected to give it to the top prosecutor.

It said it does not know why the prosecutor general did not receive it.

While the case was still unexposed in Taiwan, Swiss authorities had already opened a money-laundering probe into some bank accounts belonging to Huang.

On July 11, Liu Kuan-ping, then Taipei's representative in Switzerland, received a letter from Swiss prosecutors asking for Taiwan's assistance in the probe.

But Liu, who was appointed to the job in February and resigned on July 29, did not send the letter to the Foreign Ministry in Taipei till July 23.

Liu denied that he deliberately delayed sending the letter, according to the Central News Agency, which interviewed him in Switzerland.

He explained that the letter came as ordinary mail - it was not even registered, and there was no indication that it was meant to be secret.

Although he acknowledged the matter mentioned in the letter may look sensitive, he said he found no reason to believe that the letter should be urgently forwarded back to Taiwan.

He said he received it on Friday and did nothing about it until Wednesday, when he signed the document needed for the letter be sent back to Taipei.

But the letter did not make it to the representative office's weekly diplomatic mail bag, which had just been sent back to Taiwan. The letter had to wait for the next mail bag on July 23, he said.

"I have a clear conscience," Liu told CNA as he dismissed allegations that he intentionally delayed the letter.

Back in Taipei, Cabinet Secretary General Steve Hsueh denied that he had leaked information that led to the exposure of Chen's alleged money-laundering in the press.

He demanded an apology from Legislator Ker Chien-ming of the Democratic Progressive Party for making the allegations. Hsueh said he may take legal actions if Ker refuses to do so.

Ker was cited by the Liberty Times as claiming that the leak was the result of government manipulation, and he named Hsueh as the one who fed the press.