The Nigerian government then invited the Nigerian State Security Services and the American Federal Bureau of Investigation (FBI) to determine the cause of the crash and to confirmed if an explosion occurred in mid-flight. FBI took a piece of the burnt part, swabs from the inner and outer surface of the burnt piece and an electronic part found within the folded section of the piece of interest, back to their facilities for laboratory analysis and screened for presence of explosive residue. The results of the tests were negative (no explosion).