The cause of the crash was not immediately known. But it is the most serious yet. There is an airstrip for small aircraft in upper Montgomery, and it was unclear whether the plane was on an approach or takeoff. The case looks likely to go to a jury trial next year. He was wrong.
The cause of the crash was mostly known to the investigators.
( z0 know :ARG0 ( z1 person :ARG0-of ( z2 investigate ) ) :ARG1 ( z3 thing :ARG0-of ( z4 cause :ARG1 ( z5 crash ) ) ) :mod ( z6 most ) )
(z0 / know-01
    :ARG0 (z1 / person
              :ARG0-of (z2 / investigate-01))
    :ARG1 (z3 / thing
              :ARG0-of (z4 / cause-01
                           :ARG1 (z5 / crash-01)))
    :mod (z6 / most))
The cause of the crash was mostly known to the investigators .
z3 :ARG0-of z4
z4 :ARG1 z5
z0 :mod z6
z0 :ARG1 z3
z0 :ARG0 z1
z1 :ARG0-of z2