Subject: why does wet charcoal easily spontaneously combust?

my neighbors house fire was recently attributed to stored charcoal that had 
been out in the rain, and was drying in his attic. the fire dept said wet 
charcoal easily self ignites. i donot understand what changes occur in the 
charcoal to make this occur. can you explain? Thanks!

Re: why does wet charcoal easily spontaneously combust?