South Korean cloning pioneer Hwang Woo-Suk returned to work after an 18-day absence as a probe was launched here into the authenticity of his landmark stem cell research.
 
Hwang went into hiding after confessing to ethical lapses in his research and spent several days in hospital recovering from stress and exhaustion.
 
His return coincided with an announcement by Seoul National University to investigate allegations that his breakthrough research might have been faked.
 
Hwang arrived at his lab emerging in public for the first time since the press conference when he admitted that two of his staff had donated their eggs for his research, in violation of internationally accepted standards of medical ethics.