London's Liverpool Street station was forced to close for more than an hour on Friday evening after a large group of Facebook users descended on the concourse, mimicking a T-Mobile advert.
However, unlike the advert, the event was a "silent dance" in that no music was played, although a large amount of screaming went on.
Comments and videos on Facebook today show the crowd surfing, stripping and break-dancing. The station became so packed that police had to be called in to keep the crowds away and move dancers off the station furniture.
The dancers were drawn by an announcement on a global Facebook group page, which now has been changed.
"The Liverpool Silent Dance, this is where everyone meets at Liverpool Street station, you play your iPod, or MP3 music player in your ears and dance to your own music. We want to make this the biggest event, so please add all your friends to this group," said the organisers before the event.
The administrator of the group, which boasts more than 13,000 members, is still unknown, but goes by the name 'Crazzy Eve'.
Dancers met at 7pm under the train departure boards and kept the station closed until 8.30pm, according to eye witnesses.
Group members have complained that it was too crowded to dance properly, and that their music could not be heard above the screaming. They will have an opportunity for a rerun, as there is a similar event by different organisers planned for 10 February at another London station.
Crazzy Eve has also promised another silent dance "soon".
Facebook has just celebrated its fifth birthday, and updated its terms and conditions on Wednesday to consolidate everything users can and cannot do on the social networking site. Organising a flash mob was not listed.
The company was not immediately available for comment.
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