Davis had flown into the country after his release from a prison in Turkey
At least nine women were given a date-rape drug at a an invite-only event attended by Chancellor Olaf Scholz and MPs, his Social Democratic Party (SDP) said Saturday.
"There's quite a lot of emotion," a spokesperson for the SDP's parliamentary group told AFP, confirming a report in the Berlin newspaper Tagesspiegel.
"I advise all those concerned to file a complaint," added the group's Katja Mast on Twitter.
The spokesperson did not rule out further cases adding to the nine already declared.
The SDP sent out an email to all those invited to the party on Wednesday night condemning a "monstruous act which we immediately declared to parliamentary police".
The police would not comment when contacted by AFP.
About 1,000 people joined the chancellor and MPs at the SPD's traditional summer bash ahead of the parliamentary recess.
"It was an internal event. You could only get in with an invitation," said the spokesperson.
"There's still a lot of uncertainty, the police are investigating."
Davis had flown into the country after his release from a prison in Turkey
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