[galaxy-user] how to clear job queue?

I accidentally shut down my galaxy server in the middle of an job execution, after that I try to restart my galaxy server, it always shows the error that a job is in new state, and I can't start my galaxy server at all. I guess I have to clear that job out of the queue, so my galaxy server can start. Does anyone know how to clear the job queue? or any idea how to fix the problem? Thanks a lot!