On Friday authorities said they had discovered two further sets of DNA traces that do not match any of the others suspects' DNA, raising suspicions that more suspects are involved.
“We have to assume that we are looking at two additional suspects,” Bernd Belle from Freiburg's criminal police force said at a news conference. He said investigations were continuing.
Several men are suspected of raping the victim after she had visited a nightclub in Freiburg on October 14th.
Police said the woman had taken drugs, but that it was unclear whether a drink she took afterwards was spiked.
It is understood the woman had left the club and the main suspect, a 22-year-old man, had gone with her. The victim was then allegedly raped. The man then reportedly went back to the club where he told other men that the woman was defenceless outside, and other men reportedly raped her.
The 22-year-old suspect was described by police as a multiple offender and is suspected of being involved in another case of sexual assault.
The eight suspects in custody are seven Syrian men aged 19 to 29-years-old and a 25-year-old German.
The victim is being supported and was described by police as being in a stable condition.
'Asylum seekers should get sex education in Germany'
The human rights organization Pro Asyl (Pro Asylum) raised some concerns about the demand.
Burkhardt also warned against isolating asylum seekers in so-called anchor centres or other large shelters.