Interviews have been held and thereafter the deprivation of liberty has been lifted, says Moa Hörnquist at the Prosecution Authority's press service.
She cannot say if the men are still suspected of crime.
At 19 o'clock on Friday, the police were alerted by the healthcare system because there were suspicions that a man found in an industrial area had been subjected to a crime.
Ambulance personnel suspect that the man's injuries are not connected to an accident, says the police's press spokesperson Stefan Larsson.
The man is suspected of having been subjected to severe violence against the head.
A preliminary investigation into attempted murder was initiated. Three men were arrested during the night, but have now been released after interviews.
The injured man is being treated at the hospital with life-threatening injuries, according to Region Västmanland.
The police's technicians have conducted a crime scene investigation of the location.
