The women are believed to have been given so-called "rape drugs", ie drugs that contain substances that can put people in such a vulnerable state that the person is at risk of being subjected to sexual abuse.
- It is quite a lot of emotions, says a spokesman for the party about the incident.
After the party, which was held on Wednesday evening, the SPD sent out an email to all those invited condemning a "terrible act" and announcing that the incident "was immediately reported to Parliament's special police force".
Around 1,000 people took part in the event, which is the party's traditional summer party before the break in the Bundestag.
- It was an internal event.
You could only come in with an invitation.
There are still a lot of uncertainties, the police are investigating the incident, says a spokesman for the party.