Complex sentence: The police would close the investigation, which was never directed on any single individual, on November 21,2005, two months after the slide, citing that any unlawful acts would have happened too long before the disaster.
Split into simpler sentences: The police would start an investigation, which was never directed at any single individual, following the slide. The investigation was closed on November 21,2005, due to the fact that unlawful acts would have happened too long before the disaster.