A major U.S. daily reported Thursday that the University of Pittsburgh has launched an internal inquiry into the stem cell research of South Korean cloning pioneer Hwang Woo-suk.

The Wall Street Journal says the university launched the inquiry on the request of U.S. researcher Gerald Schatten after it learned of the duplicated photos of stem cells in Hwang’s thesis.

However, the daily noted that many renowned cloning researchers believe the thesis’ scientific conclusions to be valid.

Meanwhile, a British scientific journal has called for a review of Hwang’s work.

On its website, the Nature journal commented on a South Korean television program that had questioned the credibility of the stem cell research.

Nature pointed out that Hwang has yet to allow a thorough review of his research to clear the allegations.