MINNEAPOLIS (AP) -- As the summer campfire season picks up Minnesota Poison Control has a warning about a product used to generate colored flames.

The chemical, sold in a small foil packet, has sickened several young children in Minnesota, including one that was sent to the hospital.

The Minnesota Poison Control center has handled four poisoning cases involving the flame colorant products this season. Three cases involved the product Mystical Fire manufactured by Mystical Distributing. It contains a copper sulfate chemical that produces the coloration. The product warns against opening the package since the contents that can be harmful to children.

The center's medical director, Jon Cole, says the package can be confused with Pop Rocks or other candy. Mystical Distributing President Mark Phillips the product is tamperproof and should not be opened, but thrown directly into the fire.