The court decided that grounds for custody still existed, the spokeswoman said.
The eight former military police are indicted for war crimes against civilians in 1992 in Lora military prison in Split.
Tonci Vrkic, Ante Gudic i Andjelko Botic have been in custody since September while Davor Banic turned himself in a month ago.
Tomislav Duic, Josip Bikic, Miljenko Bajic and Emilio Bungur are still at large and a warrant for their arrest has been issued.