The girl believed to have been pushed from a balcony in an apartment block in the city’s Hermodsdal district on Sunday evening.
The suspects, both of whom are related to the victim, were arrested near the building and taken in for overnight questioning.
On Monday morning the public prosecutor ordered for them to be detained in custody on suspicion of murder or manslaughter.
“They deny committing an offence,” police spokesman Lars Karsten told TT.
Neighbours questioned by police said that there often appeared to be trouble in the fourth floor apartment.
“A lot of people have complained about noise and screaming,” one neighbour told Sydsvenskan.