The girl was questioned by authorities on Thursday after an argument at the HVB care-home the previous day led to a 17-year-old girl being taken to hospital, where she later died.
“I can't say that she confessed, but she gave information which together with other witness statements gave us a very good picture,” said prosecutor Robert Beckard. “Everything points to it being a knife wound which led to the 17-year-old's death.”
Speaking to the TT newswire, he could not share any further details about how the incident unfolded or any possible motive.
The girl is being investigated for murder or manslaughter but due to her age, she will not be tried as an adult.
“It is an extremely serious incident so we really have to investigate what happened and whether we could have acted in any way. Of course we're looking into it,” the head of the care home told local paper GT.
Criminologist Mikael Rying, who works for Swedish police and has analyzed all murder cases in Sweden since 1990, said he had no knowledge of any similar cases in recent decades. “I can't think of (any cases in which) a girl under the age of criminal responsibility has killed,” he said.
“We don't know what happened. Murder is a brutal classification for a crime, and the younger a child is, the harder is it to claim intent,” he added.
All the other children living at the home have been moved to other accommodation following the incident, local media reported.