Complex sentence: A similar accident that occurred at the same station in December 1985, which injured 54 people, was said to have been caused by a lubricant that had been applied to the tracks to test train wheels.
Split into simpler sentences: A similar accident occurred at the same station in December 1985, injuring 54 people. The 1985 crash was said to have been caused by a lubricant that had been applied to the tracks to test train wheels.