Mounties in Nanaimo have arrested two men and seized a “significant” amount of the addictive and potentially lethal drug fentanyl.

Police say a tip from the public led them to an alleged drug transaction between two men.

Officers arrested the men and a search of a suspect vehicle turned up 13 grams of fentanyl and 36 grams of crack-cocaine.

Officials are now warning local drug users that dealers may be passing off the “highly concerning” narcotic as other street drugs, such as heroin and cocaine.

“It’s still out here, so that’s why it’s significant that we got that seizure,” said Sgt. Tait Donovan with Nanaimo RCMP’s Street Crime Unit.

“[Drug users] are buying heroin thinking that it’s heroin, then we get it tested and it’s either pure or a high quality of fentanyl. Depending on the dosage, it can be fatal.”

Fentanyl, a prescription drug used mainly for cancer patients experiencing severe pain, was found in 25 per cent of the 336 illicit drug overdose deaths in the province last year, according to the BC Coroners Service.

Health officials say it is about 50 to 100 times more toxic than morphine.

“It’s a problem. It comes in waves. It’s here,” Donovan said. “We’ve seen it fairly consistently for the past 18 months. It’s been cropping up.”

Much of the supply comes from the Lower Mainland and is used as a cutting agent because it’s likely cheaper and easier to obtain, he said.

Signs of a fentanyl overdose can include severe sleepiness, slow heartbeat, trouble breathing, snoring, cold and clammy skin, and trouble walking or talking, according to the Provincial Health Services Authority.