1.   One federal investigator said Friday that the traces were found inside the rear cargo hold, toward the tail of the plane.

2.   One federal investigator said Thursday that the traces were found inside the rear cargo hold, toward the tail of the plane.

3.   The rear cargo hold is believed to have contained only cargo, not luggage.

4.   A cockpit alarm had sounded, warning of a fire in the rear cargo hold, but engineers found no problem.

5.   The rear cargo hold is said to hold no luggage.