The U.S. journal Science says controversial stem cell photos suspected of manipulation came from American scientist Gerald Schatten, not from cloning pioneer Hwang Woo-suk.

In a statement issued Wednesday, the journal said the duplicated photos of stem cells were confirmed not in the PDF file of a thesis received on May 12th, but were carried in a new file the following day after editors requested high-resolution photos from Schatten.

The journal found several of the photos from Schatten did not match those in the original thesis, and asked both professors for confirmation that day, something which unfortunately went unnoticed by the theses writers.

Science has again asked the two researchers to explain the mismatch.

Meanwhile, the magazine's chief editor Donald Kennedy said in the statement that the photos are not believed to impact the thesis' scientific conclusions.