A leading South Korean university will intensify an investigation into the country's top stem-cell scientist after reports that key parts of a landmark paper were fabricated.
The controversy concerns work by Professor Hwang Woo-suk and colleagues at Seoul National University.
Last year they published the first scientific paper on cloning a human embryo and this year displayed the world's first cloned dog.
Hwang's team said they had used their cloning method to create lines of genetically identical stem-cells from nine patients, most with a rare neurological disease. The study appeared to fulfil one promise of embryonic stem-cell research - the ability to tailor medicine to individuals.
Hwang, 53, has been under scrutiny since last month when he apologised over two women researchers donating their eggs for his work and for not providing information about that incident promptly.
Roe Jung-hye, the university's dean of research affairs, said a review team would be questioning Hwang even if he confirmed that his study had flaws.
One of Hwang's close collaborators, Roh Sung-il of Mizmedi Hospital, said "Professor Hwang admitted to fabrication," and had also told him that there were no embryonic stem cells remaining from the experiments because all the colonies had since died in the laboratory.
Roh, who was one of the co-authors of the study published last June in the journal Science, said Hwang had agreed to ask the journal to withdraw the scientific paper.
But Science said it had not yet heard from Hwang.
Reports in South Korean media said some photographic images of the stem-cell lines may have been manipulated.
Just two months ago, South Korean President Roh Moo-hyun opened a World Stem Cell Hub centre, billed as a project to put the country at the forefront of cloning research.
"I am sure anti stem-cell activists will use this to show that there are problems with this science and that it is not effectively regulated," said David Winickoff, assistant professor of bioethics at the University of California, Berkeley.
Shares in South Korean firms involved in biotechnology - a key growth area for Asia's fourth-largest economy - are down by their daily limit of 15 per cent and the overall market has been adversely affected.
The Government will decide whether to continue to support Hwang after seeing the results of the investigation.