The woman was found badly injured and severely chilled in a mining hole on Friday night.
After several hours of rescue, she could be winched up and taken to hospital.
According to the prosecutor, the woman must have been raped before she was pushed.
Suspicion was soon aroused against a man in his 40s, who was arrested on Monday.
The man is now in custody for his denial - on probable cause on suspicion of rape and attempted murder.
Holes in the fence
The mine hole belongs to the disused Långgruvan in Norberg municipality and is one of the deepest in the area - over 30 meters.
Anyone who gets to the place must drive along winding forest roads.
- You have to know the place to find, says Svante Nordström, operations manager for the rescue service in southern Dalarna who was involved in the rescue operation.
Around the old mine shaft there is a two meter high fence that will prevent accidents and intrusion.
But when the rescue service arrived at the scene, there was a large hole in the safety net.
- It was no more than three decimeters to step over.
It was not a new hole but someone had tried to fix it with steel wire, says Svante Nordström.
It would have been difficult to climb over the fence if it had been intact, he says.
- It is piled with steel bars and real fencing.
But if you really want to get in, you can of course cut it up.
What do you think it looked like this way?
- It's not good at all.
It goes without saying that it must be reviewed.
Described as "very dangerous"
Now reports that SVT has taken note of that the maintenance of Långgruvan's mining hole has been broken for several years.
After an inventory in August 2018, the hole is described as "very dangerous" by Sweden's geological survey, SGU, because parts of the fence have been cut.
During the inventory, deficiencies were found, not only here, but in the fences around several hundred mining holes in Västmanland.
The information was sent to the police in January.
SVT's review shows that the issue of responsibility for the unsafe mining holes has been discussed for a long time.
In June 2021, the situation is described as a "ticking bomb" by the police authority's internal auditors.
The description does not refer to the safety risks but to the potential expense that the work of repairing the holes would entail.
It was then written that "the tasks of fencing abandoned mining holes can to a very small extent be justified on the basis of the police's responsibility for maintaining public order and safety."
SVT has contacted the police for a comment.
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Contact SVT's reviewing reporters.