I removed an account, but I still have the messages from when the account was active and can't get rid of them.

I originally added a Twitter account to Gwibber, and the messages synced just fine, which was great. Now I decided I didn't want it to be synced with Gwibber, but after removing that Twitter account, the messages are still in my Home channel. I've tried refreshing Gwibber, but it doesn't seem to delete these messages and I've tried uninstalling Gwibber, thinking it might purge the message data and start with a blank slate, but this hasn't worked either.

Any ideas?