The US government ordered FBI agents Friday to fly to India to assist in the investigation of the bloody Mumbai attacks that killed two American travelers and a former New York couple. US citizens still in the city were warned their lives remain at risk. Intelligence officials looked urgently for clues about the identity of the attackers, a crucial unknown as Indian officials charged, without giving details, that "elements in Pakistan" were involved. A tentative rapprochement between the two nuclear-armed rivals could hang in the balance, and a US counterintelligence official cautioned against rushing to judgment on the origins of the militants. US President George W. Bush pledged cooperation with Indian authorities and mourned the deaths of more than 150 people at the hands of gunmen who attacked targets across India's financial capital starting Wednesday night. "My administration has been working with the Indian government and the international community as Indian authorities work to ensure the safety of those still under threat," he said in a statement from the Camp David presidential retreat in Maryland. "We will continue to cooperate against these extremists who offer nothing but violence and hopelessness. "