Initial reports indicated the 46-year-old woman was found dead, but subsequent information revealed that she showed slight signs of life when she was discovered by her boyfriend around 8.30pm.
She later died from her injuries at a hospital in Skövde.
Police first thought the woman may have been involved in an accident, but left open the possibility that she was the victim of crime.
Suspicions of foul play grew stronger throughout the day on Monday.
“The case is currently classified as a murder,” said police spokesperson Stefan Gustafsson to the Expressen newspaper on Monday afternoon.
The person now in police custody is being held on of probable cause of murder, reports TV4.