An interim report on the deadly April 25 crash of a speeding commuter train on West Japan Railway Co.'s Fukuchiyama Line touches on the driver's apparent erratic behavior but leaves many questions unanswered.

The report by the Aircraft and Railway Accidents Investigation Commission probing the derailment in Amagasaki, Hyogo Prefecture, was submitted Tuesday to Land, Infrastructure and Transport Minister Kazuo Kitagawa.

Its main conclusion is that speeding on the part of driver Ryujiro Takami, 23, caused the seven-car rapid service train to jump the tracks on a tight, 304-meter-radius curve and slam into a nine-story condominium building, killing himself and 106 passengers and leaving 555 people injured.