According to multiple reports of the event, male attendees found themselves approached by attractive, glamorously dressed women who were not part of the conference and who began flirting with them, touching them and handing them their cards.

Many people at the party concluded that these women were escorts. According to accounts heard by Fortune, some male attendees then mistook female entrepreneurs for escorts, and asked them if they could offer them any favors.

Get Data Sheet, Fortune’s technology newsletter.

The organizers of the event deny having had any knowledge that this would happen.

The escorts were apparently users of the app Ohlala, which is a platform for “paid dates”—CEO Pia Poppenreiter insists this doesn’t mean prostitution, though the women on the app charge hundreds of euros for a couple hours of their time.

Poppenreiter, who previously launched an app that was explicitly for prostitution (which is legal in Germany), told Fortune she was “very sorry” for what happened at the Noah conference.

“Ohlala wanted to use the Noah party for a guerrilla PR campaign,” she said, explaining that this involved getting “many of my friends” to show up. “Unfortunately, it seems to have gotten out of hand a bit…I would not have thought that this leads to such waves.”

However, attendees of the party—who wish to remain anonymous—did not buy this version of events. They noted that there were around a hundred of these women, and the party had strict entry requirements involving tickets and wristbands.

Deutsche Startups also noted that before the party Ohlala users had been sent a notification inviting them to attend. “Grab a drink & mingle with men who crave the finer things in life,” the notification read. “CEOs, executives, investors. Free entry & cocktails starting at 10 p.m.”

“These ladies were kind of attacking the men,” said one female entrepreneur. “I heard one investor came with his wife and she was really pissed.”

“One guy told me that his female employee was [approached] by some guy because they asked her if she’s also from the agency,” she continued. “In the end I was so happy that we were not dressed for a gala event. Some of them really came in a gala dress. Because we looked normal, in a normal business outfit, we were just happy we could not be [mistaken for] these ladies.”

Another female attendee said: “I do not understand how more than a hundred women, obviously escorts, got the wristbands without Noah being aware of it…I felt very uncomfortable at this event and I left early.”

Derk Marseille, a journalist and entrepreneur who was at the event, said people were “quite excited” by the number of women at the party, “since most tech conferences are dominated by male attendance.”

“It was not obvious to most men those women were escorts,” he said. “But I realized they could be after the media reports appeared.”

The Noah conference had 108 speakers on stage, 11 of whom were women. Axel Springer, which organized the conference schedule (but not the party), said this was the result of an imbalance in the startup industry that was just reflected in the lineup. As for the escorts, spokesman Michael Schneider said Axel Springer had not approved their presence.

“We didn’t know anything about that. We are irritated and are strictly against such activities. We will commit ourselves that this remains a one-time incident,” he said.

The Noah organizers issued a near-identical statement: “We didn’t know anything about that and are irritated as well. We are strictly against such activities and we will commit ourselves that this remains a one-time incident.”

However, Schneider also sent a follow-up statement: “We do not want to judge what the professional activities of the women present at the party might have been, how they might earn their money or how they presumably were dressed and what that could possibly mean. In the 21st century we don’t feel entitled to make such presumptions. To us, the insulting way of reporting about these women stands for a sexist, uptight and derogatory attitude.”

For more on barriers for women in the workplace, watch:

Two female attendees who spoke to Fortune claimed Axel Springer had sent an email to female staff asking them to come to the party, in order to increase the numbers of women there. (Fortune has not been able to verify this.) “Before the party, [the organizers] asked you to bring a guest to the party. When women asked for a plus-one they said just women,” said one.

“This is not OK for the reputation of Springer,” the other said. “We have a lot of early stage female entrepreneurs that cannot buy these very expensive tickets, and I think if you want to increase the number of women attending in the evening, why don’t they invite early stage female founders? I don’t see a reason to invite escorts to an event like that.”

“I’m not a feminist; I normally don’t get involved in discussions like that,” she said. “But this is so outdated…It’s a slap in the face for every woman that is fighting hard for a reputation in this area.”

This article was updated to correct the numbers of speakers. It incorrectly stated that there were 65 speakers, two of which were women. There were in fact 108 speakers, 11 of whom were women.

Disclosure: The author of this piece last year was an employee of Politico Europe, which is co-owned by Axel Springer. He left on good terms.