11.   -- The same explosive material -- a combination of fertilizer and fuel oil -- was used in both bombings.

12.   A computer then compares these signals to a library of signals collected by using this process on a variety of explosive materials.

13.   A critically important question, Lafflam said, was whether any of the arcane chemical compounds and highly explosive materials being stored there were unused and unneeded.

14.   But he opposed the tagging of explosive materials.

15.   But their cautionary remarks, based on the absence of even trace amounts of explosive materials, went unheeded for months.

16.   Federal officials reiterated their contention Friday that the discovery of traces of explosive material was not conclusive proof that the crash resulted from a criminal act.

17.   Five days after the crash, investigators at a makeshift lab in Calverton, N.Y., got the first positive tests for explosive materials on a piece of wreckage.

18.   For example, potassium chlorate can be combined with either aluminum or sugar to create and explosive material.

19.   From interviews with him, the authorities learned the sites of the explosive materials.