Two children needed life-saving surgery after accidentally swallowing powerful magnetic balls which are being used to mimic body piercings in a new craze.
One of the youngsters, Freddie Webster, 12, had to have part of his bowel removed as the tiny balls were ripping a hole in the wall of his stomach.
A third child, aged four, also swallowed the balls but managed to pass them out of the body naturally.
The consultant who saw them has warned parents to be aware of the new craze.
All three youngsters have been treated at Hull Royal Infirmary over the past three months.
The ball-bearing magnets are understood to have become a craze among children who use them as pretend piercings on areas such as their mouth or tongue.
However, doctors have warned if swallowed, they can cause serious damage by burrowing into the stomach and intestines.
In Freddie's case, he had put one of the 3mm diameter balls inside his mouth and the other outside but accidentally swallowed it.
Hours later, he swallowed another two and began experiencing stomach pains.
He was taken to Hull Royal Infirmary where he underwent a four-and-a-half hour operation. Surgeons removed 10cms of his bowel to enable them to extract the balls.
His mother Sarah Webster, from Driffield, said: "The surgeon came out and said that Freddie was stable but very poorly and told us the next 24 hours would be critical."
Consultant paediatric surgeon Sanja Besarovic has written to the Royal Society for the Prevention of Accidents in the hope a more public official warning can be made.
"We have been able to save these children but I'm growing increasingly concerned that this is happening often," she said.
"Both of the children recovered well after surgery but the next child may not be so lucky."