Police in Omaha have issued a public warning about counterfeit painkillers circulating in the area that investigators said have led to several overdose deaths in the city.

The counterfeit pills actually contain the powerful synthetic opioid fentanyl that is up to 100 times more potent than morphine, police said. The illegally pressed pills range in color from blue to green and have an “M” imprinted on one side and “30” imprinted on the other side, police said. The pills are intended to mimic a 30 mg dose of Oxycodone.

Officials urge anyone who comes across the described pills not to touch them and to contact police.

The Omaha Police Department said that under Nebraska law, anyone who in good faith makes a request for emergency medical assistance in response to a drug overdose and remains on scene until medical assistance and law enforcement arrive is immune from criminal prosecution.