Removing multiple entries from roster

Two of our users use Meebo widgets via the Kraken gateway. Somehow their contacts lists have accumulated 100s of Meebo guest users. I haven’t found a way to delete all of these unwanted contacts from the rosters without doing it one by one. I checked the MySQL database and in the user’s Spark folders but haven’t yet figured out where that contact information is stored. I’d really appreciate some help with this issue. Thanks.