New Jersey Poison Control is issuing a warning to parents about the dangers of button batteries and magnets.

The department says that the flat, round-shaped batteries often come in toys and games that many children received for the holidays. The coin-sized batteries pose a danger if they are swallowed.

The warning states, “Children who swallow button (disc) batteries are at significant risk for suffering serious, even deadly internal burns and injuries, in addition to choking. Parents and caregivers must be aware of this common and frequently overlooked danger around the home.”

New Jersey Poison Control says that 29 children were hospitalized this year in the state for swallowing batteries. They say that 40 children swallowed similarly-sized magnets.

“Not only are magnets a choking hazard, but if two or more magnets are swallowed together, they can attract one another inside the body, causing a blockage or twist in the intestines,” the department warned.

Experts recommend securing battery compartments on your devices to ensure kids can't access batteries.

Anyone suffering a medical emergency should call 911 right away or call the Point Control Center at 1-800-222-1222 for treatment advice.