The boy was was knifed outdoors in Vivalla, a residential area in the town, just after midnight. He was taken to the Örebro university hospital where doctors said his injuries were so serious that his life could not be saved.
“We are now questioning the suspect and any witnesses we can get hold of to bring some clarity to what happened,” said Örebro police spokesman Torbjörn Carlson at 10am on Saturday.
“I don’t want to go into details now – it’s far too early.”
The 17 year old girl was charged in her absence at first, but was then arrested in central Örebro at around 4.30am.
According to the police, there is nothing to suggest a relationship between the girl and the boy.
“We need to try to establish with our investigation the motive or underlying factors behind this,” said Torbjörn Carlsson.
The girl, who comes from Örebro, was already on police records, although not for violent crime.
The scene of the crime was cordoned off overnight and a major investigation is now underway. The boy’s body will undergo a post mortem on Saturday.