help! pcr of mtDNA control region

[Julia54601]

Our lab has a strange result from the pcr of a 500 bp region that contains
short repeat sequences.  Although we a pcr-ing from an isolated fragment,
we are getting a heavy smear above the anticipated product.  Very large --
right up to the wells.  We tried making the pcr more stringent and it
won't go away.  Has anyone ever heard of repeat sequences acting as
self-primers, sort of stringing products together?  Any advice or
speculations?  Please send e-mail to my address:  Julia54601 at aol.com.