Investigators believe the most likely hypothesis is that Lucía died accidentally after wandering off from the terrace where her parents were having dinner on Wednesday night.
Sources close to the case told local media that the post mortem results showed injuries consistent with being hit by a train and that no wrongdoing by a third party was suspected.
Lucía was playing with cousins near the bar restaurant next to the station in Pizarra where her parents were chatting with other family members.
But after losing sight of her, they raised the alarm at 11.25pm and sparked a search involving 600 rescue service members and volunteers, that lasted all night.
The little girl's body was eventually discovered at 7am on Thursday morning lying lifeless alongside a railway track some three kilometres along the tracks from the restaurant.
A train driver spotted what he thought could be a body alongside the track and stopped the train to alert authorities, according to a report in the local Diario Sur.
It is thought likely that the girl became disorientated and couldn't find her way back, walked three kilometres along the tracks until she felt sleepy and lay down.
It is likely she killed when hit by the first train of the morning which passed Pizarra at 6.45am but wasn't spotted until that same train – driven by the same driver - made the return journey at 7.15am.
Residents in Pizarra, a town of 9,000 residents to the northwest of Malaga have been devastated by the death and three official days of mourning have been declared.
The funeral is taking place on Friday.