NEW : Swiss government calls for swift investigation . Police say a woman was gang - raped in central Zurich . The victim and her husband were camping . The victims went to police and the woman was hospitalized and later released . 20 people have been detained for questioning .
NEW : Swiss government calls for swift investigation . Police say a woman was gang - raped in central Zurich . The victim and her husband were camping . 20 people have been detained for questioning .