Abbotsford police say they’ve witnessed a “concerning” jump in the number of heroin overdoses in the Fraser Valley community.

“While the exact numbers are still being gathered, the increase in calls for assistance related to these medical emergencies could be as high [as] 39 per cent,” Const. Ian MacDonald said in a release.

One person has died in eight overdoses since mid-May, but most cases have resulted in "medical emergencies," MacDonald said, including one case that came in after an initial press release was sent out Wednesday.

He said drug users have told officers they’re concerned about the potency of heroin that’s currently being bought, sold and used.

One reason for the heroin’s increased potency and overdoses could be the presence of fentanyl in the drug, MacDonald said.

The dangerous painkiller, which is exponentially more powerful than heroin, was blamed for a spate of overdose deaths in B.C. in May.

Provincial health officer Dr. Perry Kendall warned that drug users taking the opioid might think it’s heroin or oxycodone as they cause nearly identical symptoms – but fentanyl taken in equivalent amounts is likely to cause an overdose.

MacDonald said a sample of the heroin has been obtained and sent for testing, and in the meantime illicit drug users should exercise extreme caution and call 911 with any signs of medical distress.

“Heroin users should never shoot up when they are alone and are urged to call immediately for medical attention if they feel unwell, or believe the may be having adverse effects after using,” he said.

Local users and their supporters have seen the tainted heroin in action and said it takes only moments for the drug to send someone spiraling into an overdose.

“Inexperienced people just tend to end up doing a little too much, what seems to be a regular amount and all of a sudden, you check over on them and they’re not breathing,” said Daryl, who didn’t want his last name used.

Daryl said he knows six people who have overdosed from the dirty drugs and he has also been a victim after only taking a tenth of a gram, which is just a fraction of his daily heroin intake.

"I actually OD’d myself two weeks ago. I woke up in the hospital,” he said. “If you get it, don’t do it. Go somewhere else man. I found out for myself.”

Michele Giordano of the Fraser Valley Women’s Resource Society said she came in to work one morning when a woman told her to call 911 – a man had dropped to the floor after using the tainted drug.

“There’s been a number of people that we support that have experienced the same overdose,” Giordano said. “We’ve been warning people about the heroin for a month now.”

She added that if the man hadn’t been in the centre while overdosing, he would have died.

“We’re really quite concerned. We don’t want our friends to die out here,” she said.

In nearby Vancouver on Saturday, ‘Glee’ actor Cory Monteith was found dead in his hotel room after overdosing on heroin and alcohol, but BC Coroners Service spokeswoman Barb McLintock confirmed fentanyl was not a factor in his death.

"Mr. Monteith died of a mixed-drug toxicity, involving heroin and alcohol," she reiterated.

MacDonald said there's always a chance fentanyl-laced heroin could make its way beyond Abbotsford.

“Based on my knowledge as a police officer, drugs are going to be distributed where there’s money, and suppliers are going to take their product wherever they can,” MacDonald said.

“I believe that if there is a bad batch of heroin, it could be impacting people across the Lower Mainland and not just in the City of Abbotsford.”

With a report from CTV British Columbia's Jon Woodward