McDonald's is recalling 12 million "Shrek"-themed drinking glasses in Canada and the U.S. because of cadmium in the painted design.

The glasses were sold as part of a promotional campaign for the movie "Shrek Forever After." All four designs depicting the characters Shrek, Princess Fiona, Puss in Boots and Donkey are included in the recall.

Customers are instructed to stop using the glasses immediately. McDonald's says information on how to return the glasses and get a refund will be released shortly.

The U.S. Consumer Product Safety Commission issued the warning Friday, noting there have been no incidents of illness reported.

It noted that "long-term exposure to cadmium can cause adverse health effects." Cadmium, which is used to create reds and yellows in some paints, is a known carcinogen that can also cause bone softening and severe kidney problems.

The cadmium could leach from the paint onto a child's hand then enter the body when the child puts that hand to his or her mouth, said CPSC spokesman Scott Wolfson.

"A very small amount of cadmium can come to the surface of the glass, and in order to be as protective as possible of children, CPSC and McDonald's worked together on this recall," Wolfson told the Associated Press.

McDonald's USA spokesman Bill Whitman said his company believed the Shrek glassware was safe for consumer use. "However, again, to ensure that our customers receive safe products from us, we made the decision to stop selling them and voluntarily recall these products," he told AP.

Wolfson would not specify the amounts of cadmium that leached from the paint in tests, but said the amounts were "slightly above the protective level currently being developed by the agency." He noted the glasses have "far less cadmium than the children's metal jewelry that CPSC has previously recalled."

McDonald's Canada says the voluntary recall was made "in an abundance of caution" following consultations with Health Canada. It says the recall was issued after it learned of changing assessment of standards for cadmium in consumer products in the U.S.

McDonald's Canada says the glassware was evaluated by an independent third-party laboratory when it was made and distributed and was in full compliance with all applicable Canadian requirements.

The recall was set in motion by an anonymous tip to Rep. Jackie Speier last week. She alerted the CPSC, which tested the glasses and confirmed the presence of cadmium in the paint.

The glasses were manufactured by ARC International of Millville, N.J., and were sold from May 21 into June. It's not clear where the paint used on the glasses was manufactured.

Roughly 7 million of the glasses had been sold. Another 5 million are in stores or had not yet been shipped.

With a report from the Associated Press