Michael Callahan, the Yahoo executive vice president who has been criticized for his role in the 2004 imprisonment of a Chinese dissident, issued an apology on Thursday ahead of a congressional hearing next week. Callahan admitted that he was sorry for failing to tell US lawmakers that Yahoo knew more than he initially acknowledged in testimony last year about the investigation into Shi Tao, a journalist now serving a 10-year prison sentence. According to US lawmakers, the authorities only tracked down Shi after Yahoo divulged his e-mail account, IP address log-on history and the contents of his e-mail messages. Congressmen have claimed that the US internet company had a Chinese government order requiring information on a Yahoo user suspected of having "illegally provided state secrets to foreign entities," a charge often used to prosecute political dissidents. However, when he testified last year, Callahan said Yahoo had "no information" about the investigation. The order was finally made public by a San Francisco-based human rights group, the Financial Times reported.