Originally Posted by forget
Which bit is baffling you?
NTSB officials suspect that the fire may have been started by a cigarette in a back-cabin lavatory.
...... concludes that the possibility that this occurred cannot be ruled out.
Your comprehension of English appears to be distorted by your desire to prove something which is in fact unproven.
Not ruling out a
possibility is not akin to
suspecting it to be the cause. And the NTSB didn't even do that (see
may).