U.S. lawmakers have joined North Korean defectors in urging China not to return refugees from North Korea to their homeland.

The U.S. Congressional Executive Commission on China held a hearing Monday to highlight the urgency of the situation of dozens of North Koreans who recently fled into Chinese territory.

Representative Chris Smith, a Republican from New Jersey and the head of the commission, says that in recent weeks Chinese authorities have detained potentially more than 40 North Koreans who have escaped to China. He says North Korean leader Kim Jong Un has threatened to kill three generations of any family with a member caught defecting from North Korea during the 100-day mourning period for his father, the late ruler Kim Jong Il.

North Korean defector Han Songhwa testified before the committee Monday, saying the sole wish that led her to escape was to feed her children. She says she was forcibly repatriated back to North Korea four times before she escaped overseas. She said the returned defectors had to live like animals in North Korean prison camps in order to survive.

According to the State Department's 2010 report on human rights, it is estimated that thousands if not tens of thousands of North Koreans are hiding in China. Reports and testimonies of those who have been forcibly repatriated detail a wide range of punishment for those who are caught, including beatings, torture, forced labor and sexual violence.