It is unclear whether the woman may have been already deceased when struck by the train.
Const. Carl Kennedy says police were called around 10:30 p.m.
The conductor and the engineer told officers that the woman's body was on the tracks about a kilometre east of the Interior city, and they were unable to stop in time.
Several train cars rolled over the victim, whose body was found under the 11th car.
Kennedy says police have an onboard train video that shows the woman laying on the track as the train approached.
Police are trying to identify the victim by tracing a bank transaction record found on her body. (CHNL)