The coauthor of a controversial Japanese paper on stem cells said today third-party tests show no evidence to support the existence of so-called STAP cells.

University of Yamanashi Professor Teruhiko Wakayama announced the findings at a press conference. Wakayama also apologized.

Wakayama said testing showed the STAP cells created by researcher Haruko Obokata differed genetically from the mouse strains he provided for use in the research.

This is the latest development in the controversy surrounding Obokata.

Obokata was lead author of an article published in British science journal Nature in January.

Her paper described an easy new way to make stem cells with great potential for generating organs for sick people.

Obokata later retracted her paper amid allegations she doctored the research.