abnormal data grow

Hi,

I have been having this problem where the database size suddenly grows
from the normal size of about 300Mb to 12Gb in one night.
When I look up the table size, the biggest one is only 41Mb and the
total of all table size is only 223Mb.
But in the filesystem data directory the total size is 12Gb. I noticed
there are 10 files with 1Gb size each:
1.1G    25677563
1.1G    25677563.1
1.1G    25677563.2
1.1G    25677563.3
1.1G    25677563.4
1.1G    25677563.5
1.1G    25677563.6
1.1G    25677563.7
1.1G    25677563.8
1.1G    25677563.9

So I tried to find out what table that is, but this query return nothing:
SELECT relname, relpages
    FROM pg_class
    WHERE relname = 'pg_toast_25677563' OR relname =
'pg_toast_25677563_index'
    ORDER BY relname;

and if I run this query:
SELECT relname, relpages
    FROM pg_class ORDER BY relpages desc

the top ones are these tables (which is not the id of the 1.1 Gb files)
pg_toast_25677561                                               1382845
pg_toast_25677561_index                                     22116

I'm just wondering is there a way to know what that 25677563 file is?
Why does postgres create a copy of that file with .1, .2, .3, etc. Is
that file still in used (because I can't find it in the pg_class table)?
Will postgres clean the database up or should I do a manual clean?

- reynard