YONKERS, New York: After testing discovered harmful levels of heavy metals in chocolate, consumer magazine Consumer Reports has urged four chocolate producers to reduce the amounts of lead and cadmium in their dark chocolate products by Valentine's Day.

Long-term exposure to the metals can result in nervous system problems, immune system suppression and kidney damage, said Consumer Reports in letters to Hershey, Mondelez International, Theo Chocolate and Trader Joe's, which were accompanied by nearly 55,000 petition signatures.

The risks were higher for pregnant women and young children because of the risk of developmental problems, the letters stated.

In December, Consumer Reports said of the 28 dark chocolate bars it tested, 23 had potentially harmful levels of lead, cadmium or both for people who eat more than one ounce of chocolate a day.

Many consumers eat dark chocolate for its potential health benefits and relatively low sugar levels, but "there is nothing healthy about ingesting heavy metals," the magazine added.

Trade group National Confectioners Association said that California health guidelines used by Consumer Reports considered "the most protective available and are not food safety standards," adding that chocolate are still safe to eat.

Since Consumer Reports released its study, Trader Joe's has been sued at least nine times by consumers due to potential heavy metals in its dark chocolate.

Hershey's and Mondelez have also been sued over the magazine's findings, as well as other chocolate makers, including Godiva and Lindt.