Five of the boys are suspected of aggravated rape of a child aged 15 or younger and the other three are accused of participating in other activities linked to the incident last summer, reported the Aftonbladet daily on Wednesday.
It is understood all eight teens deny the accusations.
"I can say as much as that the men deny any crime. But I can't elaborate on what they have said during interrogations," prosecutor Jonas Martinsson told regional tabloid GT.
Little further information was available about the case on Wednesday, due to the age of the victim and alleged perpetrators.
However, Swedish media reported that the teenagers are all believed to be born between 1998 and 2001 and are based in Gothenburg.
"This is a situation where all are children, I would say, so to speak. Something has happened and he absolutely denies any crime. What they have done, they have all been in on together, on a voluntary basis that is. He denies any involvement," Edip Samuelsson, a lawyer representing one of the suspects, told GT.
"It is said to have taken place in August, and it is February now. I am sure there are underlying causes, but the investigation will have to demonstrate that."
Detention hearings are expected to be held on Friday.