URGENT TriggerStore Files Not getting removed

We are having strange problem with triggerstore files not getting removed. We started noticing the same from mid of december that there
are triggerstore files in the DocumentStore Folder not getting removed
and that degraded the server performance and ultimately we had a severe downtime on production box.

We shutdown the broker after 15 min we shutdown the IS and then removed all the files and from the folder and restarted and it worked fine now there are again few files sitting in that folder for 17th,18th and 21st Jan, 2005.

We are having IS 6.0.1 and Broker 6.0.1 running on HP-UX.

Please anyone face this problem or any IDEA please tell me the reason for this.