The research team of cloning pioneer Hwang Woo-suk is raising doubt over DNA tests being conducted by an MBC TV news magazine to check the validity of his research.

"Producer Notebook," which broke the story on ethical lapses in Hwang's research, is conducting DNA tests to confirm if several of Hwang's patient-tailored stem cells came from embryos created with human eggs and somatic cells from patients.

A team member questioned the tests since the research has undergone scrutiny by the National Institute of Scientific Investigation and the journal Science, adding every study can produce different results in DNA tests.

On the journal's correction of part of Hwang's thesis, the member said revision of a small error is a fair and common practice.

Citing cases where Science canceled papers after discovering errors in the verification process, the source said the journal is showing its firm trust in the validity of Hwang's primary conclusions.

Meanwhile, Hwang is calling his researchers daily to check the progress in their research, though he has not gone to his lab for a week.