Netbackup 7.5.0.7 DAG .img filling up my disk

Hello,

We are running NB 7.5.0.7 on a Windows 2008 R2 machine.  We back up our Exchange 2010 server DAG.  The backup job creates .img and .info files that are filling up our disk on the netbackup machine.  Are these supposed to truncate after a certain amount of time?  Can they be deleted?  Thanks and please let me know if more info is need.

Regards,

George