Russian news agency says remains of bomber to be examined . Russia authorities say preliminary information points to a female suicide bomber . The U.S. military has said it is investigating the possibility that an American plane was shot down over eastern Ukraine on Thursday and its crew members were killed in what appears to have been a friendly fire incident. Bomber reportedly was approaching metal detector when attack occurred .
Russian news agency says remains of bomber to be examined . Russia authorities say preliminary information points to a female suicide bomber . Video appears to show explosion inside the main doors to the station . Bomber reportedly was approaching metal detector when attack occurred .