TORONTO, Sept. 2 (UPI) -- Thousands of sets of pencils sold in Canada are being recalled because of high lead content in the coating.

Health Canada issued the recall, saying the sets have more than 600 milligrams of lead per kilogram, which means they cannot be sold or advertised, the Canadian Broadcasting Corp. reported.

Health Canada said the pencil sets have been sold since January of this year.

The pencils, which are manufactured in China, do not pose a risk unless a child chews or sucks on them, the CBC reported.

Health Canada warned children and parents that even short-term exposure to high lead levels "can cause vomiting, diarrhea, convulsions, coma or even death."

No incidents of injury caused by the pencils have been reported.