Police began clearing tents from the Occupy San Francisco camp early Wednesday.
Police began the operation at about 3 a.m. The Associated Press said that several hundred people had taken up residence at a downtown plaza.
Radio station KCBS reported that several tents were taken down and that protesters had been allowed to retrieve their belongings and leave before authorities moved in.
It was not immediately clear whether there had been clashes, injuries or arrests, the Associated Press reported.
However, the Occupy California Twitter account said 15 people had been arrested and "protesters possessions being disposed of."
Attempts to reach police for comment were not immediately successful.