Power project massive increase in file size

Any body here has any idea about what is it in a power project programme that takes most of the disk space. I have been working on a programme that was eariler of a size 4 mb but has jumped to 14 mb in the next revision although i have just added 200 more tasks making them from 2100 to 2300. Now, i have tried to delete every thing that i could imagine being the reason behind the massive increase in size. Have tried deleting resources, calendars, saved views, etc nothing seems to work. Have called up Asta support several times but no body there knows the apparent reason.Anyone here could help me out?