A dangerous new form of fentanyl — dyed and shaped so it looks like candy or children’s chalk — has made its way to the Pacific Northwest, according to the Pierce County Sheriff’s Office.

In Oregon and at the United States’ southern border, law enforcement officers recently seized “rainbow fentanyl” in two forms: pills that could be mistaken for candy and pressed blocks that look like sidewalk chalk, the Sheriff’s Office said.

Fentanyl is a synthetic opioid that is 50 times more potent than heroin and 100 times more potent than morphine, according to the U.S. Drug Enforcement Administration. Just two milligrams of fentanyl, equal to 10 to 15 grains of table salt, is considered a lethal dose. It is the deadliest drug threat facing the country, the DEA said in a statement.

The shapes and colors used have law enforcement concerned that children may mistake it for candy or a toy, and also that teenagers could be more tempted to try the drug, the agency said.

Parents are urged to be on the lookout for suspicious substances in public play spaces and to talk to their children and teens about the dangers of fentanyl and other drugs.