Complex sentence: In the formal investigation of the accident there were three possibilities proposed for what could have caused the ignition of the blasting powder: electrical sparks or current, open lanterns, and lighted tobacco pipes.
Split into simpler sentences: In the formal investigation of the accident there were three possibilities on what could have caused the ignition of the blasting powder. The theories proposed were ignition caused by electrical sparks or current, open lanterns, and lighted tobacco pipes.