The MBC network previously broadcast a programme questioning how human eggs used in the work of Hwang Woo-suk, the scientist who brought South Korea to the global forefront of stem cell and cloning research, were procured.

MBC did not say when it would air the second programme, but producers would like to broadcast it soon.

The producers said they believed a study by Hwang's team could be flawed. In the study, published earlier this year in the periodical Science, Hwang detailed how the team took skin cells from donors to produce tailor-made embryonic stem cells.

The research made headlines around the world amid hopes that it could eventually help lead to cures for deadly and debilitating diseases such as Parkinson's.

'The stem cells provided to us by Hwang's team did not always match the donor from which they were supposed to have come, based on DNA testing,' Choi Seung-ho, a chief producer at MBC, told a news conference.

Officials from Hwang's team said they were not aware of the details of the MBC investigation and could not comment.

Hwang's team has said their work was vetted by a strict and well-established system of peer review before it was published.

Choi said the network was 'not 100 percent sure' of its results, but testing done by independent labs on cells provided by Hwang's team indicated that the donor's DNA and the DNA of the stem cell line did not match in a few cases.

Hwang is considered a hero in South Korea for making the country one of the world's leaders in stem cell research.

After airing its first story last week about ethical lapses, MBC was picketed by protesters and some companies pulled advertising.

'MBC has become the subject of strict criticism with charges of us trying to undercut out nation's interest through our reports,' Choi said.

Hwang apologised last week for ethical breaches in his research, in which two junior associates donated egg cells to advance the team's studies. He also apologised for not releasing information about the incidents in a timely fashion.

The international scientific community frowns on donations by research associates because of the possibility of coercion.

Since his apology, Hwang has been out of the public eye and, according to media reports, is staying at a Buddhist temple.

Source