As a Weight Watchers group gathered for a routine weigh-in, the dieters got an idea of how far they still had to go: The floor underneath them collapsed, a Swedish newspaper reports.

"We suddenly heard a huge thud; we almost thought it was an earthquake and everything flew up in the air," one of about 20 group members said to the Smalandsposten newspaper. "The floor collapsed in one corner of the room and along the walls."

After the initial collapse on Wednesday evening, the floor started to cave in other parts of the room, and the stench of sewage crept into the clinic, which is in Vaxjo, a city in south central Sweden. The group is looking for an alternate location for future meetings, Weight Watchers consultant Therese Levin told the Swedish paper.

No one was injured, and the cause of the collapse is still under investigation.

Afterward, the participants moved the scales to a hallway to have a real weigh-in. That time, the floor held.