A former assistant of disgraced scientist Hwang Woo-suk has denied switching embryonic stem cells with ordinary ones from MizMedi Women's Hospital in Seoul.

Park Jong-hyuk, now at the University of Pittsburgh, was quoted by his wife in a KBS phone interview Wednesday that he is angry over Hwang's allegation.

She said her husband had believed Hwang had stem cells right before the investigative panel's announcement this week, and that he had told the panel last month that Hwang's team would show data proving the cells' existence.

She said Park was surprised to hear the panel's conclusion that the stem cell reported in the 2004 Science paper was not produced from cloning but from parthenogenesis.