The boy is thought to have been murdered at the weekend, though it was not until Tuesday that police began to suspect that a crime had been committed.
“A little boy has been killed. There is a woman who has been taken into custody on suspicion of murder,” police spokesman Thord Haraldsson told TT. .
The boy was taken to hospital in the early hours of Sunday morning where he later died, Sveriges Radio reports.
“It has been ascertained that his injuries must have been caused by another person,” Haraldsson told newspaper GT.