The suspected culprit of a train crash in Australia earlier this week is a big infestation of millipedes that caused a "slippery mess" on the tracks, according to Reuters.

The official cause of the crash has not yet been determined, but investigators are looking into the millipede theory after they found hundreds of millipedes squashed on the tracks.

Six passengers were injured in the crash, which occurred after a train pulling into a station in western Australia ran into a stopped train.

This wouldn't be the first time Black Portuguese millipedes caused problems for trains. In 2009, thousands of millipedes took over a large section of train tracks in Australia, causing cancellations and delays.

In regard to this week's crash, Public Transport Authority of Western Australia spokesman David Hynes told Reuters: "What happened in previous instances is trains which were travel ling at speed have gone over an infestation, crushed them and made the tracks slimy. The train loses traction and the train has slipped."

The millipedes are considered an invasive pest in Australia.