China has censored a letter signed by 100 alumni of a top university calling for a central government probe into the case of a mother of eight who was kept chained by the neck in a hut, a rare public challenge to the government of President Xi Jinping.

The graduates of Peking University called for an investigation of local officials involved in the case, a nationwide review of women and children involved in trafficking cases, and changes to the law to prevent future such incidents. They also wanted more details released on the woman’s identity. ..