A Prague hospital said on Friday it was treating five children who had swallowed magnets following a “piercing challenge” they had found on TikTok.

The children placed sphere-shaped magnets at the tip of their tongues to imitate piercing and then swallowed them by accident, the Prague-Motol hospital said in a statement.

“One patient was lucky enough to excrete the magnets easily, but other patients remain in hospital and two are likely to undergo acute surgeries today,” added the hospital in the Czech capital.

The hospital said patients who swallowed several magnets or a magnet and a metal object ran the risk of the objects connecting inside the body.