Police in Vancouver are urging caution after a spike of suspected fentanyl overdoses.

A total of 16 people overdosed Sunday, including six between 7:30 and 8:30 p.m.

No fatalities have been reported, but officials are appealing to drug users to be extremely cautious as tainted heroin is likely spiked with the powerful opioid.

All of the ingested drugs were the colour pink.

“The toxic substance has yet to be determined, but it is suspected that fentanyl may be the cause,” said Sgt. Randy Fincham.

Police are now trying to determine if the drugs came from the same source, and attempting to track where it came from.

“It’s very challenging to determine the source of something like this,” Fincham said.

“Much of the drugs coming to Vancouver come from overseas, but certainly isolating in any given community where this drug is and stopping it at the source before it gets to the general public is the goal.”

The powerful painkiller is being blamed for a spike of overdose deaths across Western Canada, including four in British Columbia.

"This is a huge problem. It continues to grow," Fincham said.

The cheap drug, a prescription drug used primarily for cancer patients in severe pain, is being added to recreational drugs, and can lead to an almost immediate overdose death. It is roughly 50 to 100 times more toxic than morphine.