CINCINNATI -- When parents buy toys with small magnets used to join pieces, they will probably see the choking hazard warning on the box.

But an Ohio doctor said there's another danger if a child swallows the magnets. Dr. Alan Oestreich said seven children have been treated for internal damage caused when more than one magnet was swallowed.

He said that the magnetic attraction is so powerful, the pieces will actually rip through tissue.

"The blood supply where they're stuck together gets cut off, and then the tissue gets thick and magnets may travel through the bowel wall," Oestreich said.

In one case, he said, a child swallowed nearly 30 of the small magnets.

"The surgeons had to sew up part of the bowel, remove part of the bowel and after several days of recovery, the child did well," Oestreich said.

Oestreich has been leading the charge to get toy manufacturers to put a warning on the package, which should come by the first of next year.

Oestreich said that when swallowed, these toys could cause flu-like symptoms.

If you think your child may have swallowed them, ask for an X-ray of their stomach.