The alarm to SOS came in shortly after lunch on Friday.
A report of grievous bodily harm has been made and one of the boy's guardians is suspected.
Otherwise, the police do not want to leave any details about the incident.
- There will be a call via SOS 112, but I can not comment on who it is that has alerted, says Rickard Lundqvist at the police command center to SVT Nyheter Småland.
Has been taken to Lund for further care
On Friday evening, the Kronoberg region describes the boy's condition as stable.
During the afternoon, he received intensive care in Växjö and has now been taken to the intensive care unit at the children's and adolescents' hospital in Lund.
The incident occurred in the Arab area.
The police are currently very scarce with information about the circumstances.
- A prosecutor-led preliminary investigation has been initiated, says Rickard Lundqvist.