New allegations of fraud in stem-cell research by a prominent South Korean researcher emerged Thursday, and scientists said his other high-profile claims could face investigation as well. Among them: the first cloned human embryos and the first cloned dog.

The reputation of Hwang Woo-suk of Seoul National University has been battered by allegations of fabrication in a blockbuster paper published in May. He and co-authors claimed that by cloning human embryos, they had created 11 stem cell lines that genetically matched certain patients.

Scientists hope to use such "therapeutic cloning" someday to create tissue for transplant into people with illnesses like diabetes and Parkinson's disease.

Hwang's paper appeared in the journal Science. In a letter released earlier this week, Gerald Schatten of the University of Pittsburgh asked Science to remove him as senior author, saying he had learned that "certain elements of the report may have been fabricated."

On Thursday, a South Korean television station reported that a co-author of the paper said Hwang had pressured a former scientist at his lab to fake data for the report. Nine of the 11 cell lines were faked and the authenticity of the other two was unknown, the co-author said.

Hwang has reportedly agreed to ask Science to withdraw the paper, but the journal said Thursday it had received no such request.

The South Korean government said Friday that a scientific review must be conducted to determine the veracity of Hwang's research. Following an emergency meeting chaired by Prime Minister Lee Hae-chan, the government said it would wait for an internal probe by Seoul National University.

Despite the revelations, the South Korean government will still "provide support to research and development to insure our country's research in related fields is not undermined," said Kim Chang-ho, head of the Government Information Agency.

Donald Kennedy, editor of Science, said the journal welcomes inquiries by authorities in Korea and at the University of Pittsburgh. Hwang did not answer his phone and researchers from his lab could not immediately be reached for comment.

Douglas Melton, co-director of the Harvard Stem Cell Institute, said Thursday through a spokesman that he was "truly saddened" to hear of the report from South Korea, "which if true, is tragic. But stem cell science holds too much promise to allow this incident to detract from the careful, closely supervised work being done in the U.S."

Some other scientists stressed Thursday that the fraud accusations against Hwang are not proven.

"We have to give him the benefit of the doubt right now," said cloning researcher Peter Mombaerts of Rockefeller University in New York.

He said Hwang and a colleague appeared confident and believable when top cloning researchers questioned them about the work at a scientific meeting that took place Nov. 9 before the accusations arose. "They withstood the test," Mombaerts said.

But if substantial fraud is proved, scientists said, it would cast doubt on Hwang's other work, including his report last year of the first cloned human embryos from which stem cells were extracted, and his announcement in August of the first cloning of a dog.

"If the accusations of fraud are documented, I think every one of his papers has to be called into question, from the time he was a student," said Dr. Gerald Fischbach, executive vice president of the Columbia University Medical Center in New York and an outspoken supporter of stem cell research.

"It's very natural to begin to question one's other work if something like this shows up in a particular piece of work," said Mark S. Frankel, director of the scientific freedom, responsibility and law program at the American Association for the Advancement of Science.

Unless other papers are examined "you never really know" if they're fraudulent or not, and "it will be a cloud not only over the scientist but also the (scientific) literature."

So "it's prudent to do that kind of review of other papers," particularly those related to the topic of the initial paper, he said. Universities and journals in the United States typically conduct such reviews, he said.

Dr. Steven Hyman, provost of Harvard University, stressed that he would not comment on Hwang's case specifically but said in general, "people who commit clear scientific fraud of the worst sort, which is data fabrication, for example, have often done it more than once."

Just because a paper appears in a prestigious scientific journal doesn't guarantee it's correct, although outright fraud is rare. Submitted papers are subjected to peer review, which means experts examine the manuscript to look for logical errors and whether its methods are reliable, for example.

"It's not a forensic review, it's a review that assumes that the authors submitting the research are telling the truth," said Curt Civin of Johns Hopkins University Medical School, editor of the journal Stem Cells and a reviewer for other journals.

Once a significant paper is published, other scientists try to reproduce the results or carry out other experiments that will indicate whether the finding is valid. If those experiments don't support the original one, questions arise.

"Science is a self-correcting enterprise and it's very hard for fraud or wrong results to be propagated. In fact, it's impossible," Fischbach said.

But Civin said that when it comes to work with human stem cells, "that mechanism of science has been paralyzed artificially by the inability of us in the U.S. to do these kinds of experiments." That's due to restrictions on federal funding for human embryonic stem cell work, he said.