TWA 800 Graphics and Simulations indicate probable cause:

Date:         06 Aug 98 11:26:39 
From: (WSherr6080)
Organization: AOL
Followups:    1
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Graphics of the debris field appearing in "Newsday" and the "Press
Enterprise" newspapers, based on NTSB specifications of the FDR
readouts; and the NTSB simulations of the accident, indicate an initial
breakup prior to the explosion.  A streaming fire from the lower
fuselage appears at the same time and 4 seconds later the explosion
occurs and the forward 70 feet of the aircraft nose structure is severed
from the fuselage.  This flame front is the probable ignition source for
the center fuel tank.