Posted Wednesday, August 1, 2012 --- 12:19 a.m.

NEW YORK (AP) -- Scientists have found new evidence for a theory about why some cancers return after they've seemingly been wiped out. Three studies in mice say tumors contain a pool of cancer stem cells that can multiply and seed the tumor's regrowth.

If that's true, scientists will need to find a way to kill those stem cells, in addition to how they attack the rest of the tumor.

Researchers have been finding signs of this stem cell idea for about a decade. The new studies by three teams of scientists take a different approach in analyzing tumors of the brain, skin and colon in mice. The work was published online Wednesday by the journals Nature and Science.

Copyright 2012: Associated Press