ISLAMABAD (Reuters) Police have arrested 30 suspects in connection with a bombing that killed three American soldiers, three children and a Pakistani paramilitary soldier outside a girls school, an officer said. Naeem Khan, duty officer in the police station in the town of Timergara where the attack took place, said police suspect the Wednesday bombing was a suicide attack. We have recovered the engine of the car we suspect was used in the bombing, Khan told Reuters. Taliban claimed responsibility for the attack and threatened more attacks on Americans. We have also found some limbs which we suspect are of the bomber. We have sent these limbs for DNA tests, Khan said. Taliban have bombed markets, schools and military and police facilities despite major government security offensives that have destroyed some of their bases. The three US soldiers were part of a small unit that trains Frontier Corps responsible for security in northwestern areas near the Afghan border seen as part of a global militant hub. They were on their way to attend the opening of a girls school that had recently been renovated with US humanitarian assistance when the bomb exploded, leaving a crater a few feet away from the school.