At least one of the recent ecstasy-related deaths in the Lower Mainland has been linked to the same potent neurotoxin found in five overdoses in Calgary, health officials say.

Provincial Health Officer Dr. Perry Kendall told reporters Thursday that one of the four young people who have died after taking ecstasy in the last two months consumed a pill containing paramethoxymethamphetamine (PMMA), a toxin that can lead to seizures and dangerously elevated body temperatures.

"[PMMA] is considerably more neurotoxic than MDMA is," Kendall said, referring to the active ingredient in ecstasy.

He added that there is a possibility some of the three other recent deaths are also associated with PMMA, but the coroner's office hasn't completed its investigation into those cases. While the same chemical has been linked to ecstasy-related deaths in Calgary, investigators don't yet know if the drugs are from the same batch.

Kendall says that PMMA causes a "storm" of the neurotransmitter serotonin that is difficult for the brain to process and that it takes longer for users to feel the effects of the drug than pure ecstasy does.

"The onset is very slow to start with, so they start taking more pills," Kendall said.

A total of 16 people died in B.C. after taking ecstasy last year, and health officials will now take a second look at those cases to see if PMMA was a factor.

"We don't really know if PMMA was present in 2011 because we weren't testing for it," Kendall said.

Police and medical specialists have been warning Metro Vancouverites to stay away from ecstasy after the recent spate of deaths.

A 22-year-old Vancouver woman died this weekend after taking ecstasy at a house party following similar tragedies that claimed the lives of 20-year-old Tyler Miller on Nov. 27, 17-year-old Cheryl McCormack on Dec. 20 and an unnamed Burnaby resident who ingested ecstasy on New Year's Eve.

A 24-year-old Abbotsford resident was also rushed to hospital in critical condition on New Year's Eve after taking ecstasy with friends, who say she may have taken more of the drug than they had.

The overdoses mirror a similar trend in Calgary, where five people have died after taking ecstasy in recent weeks. On Wednesday, a coroner in the Alberta city confirmed that PMMA and methamphetamine were present in the toxicology reports for each of the victims.

Police say that PMMA and methamphetamine have not previously been found in ecstasy sold in Calgary.

Health officials say that the majority of ecstasy on the streets of B.C. is contaminated with other drugs like methamphetamine, ephedrine, ketamine and PCP.

"The best advice is, don't take illicit drugs," Kendall said.

"If you still feel you have to take these drugs, never take more than one and have a sober person with you."

He pointed out that because ecstasy is usually manufactured in a bathtub, the composition of one pill won't necessarily match up with another from the same batch. He said that the drug can also affect different people in different ways depending on a number of factors, including the prescription drugs they may be taking.

"There's a possibility we have different genetic pathways for breaking down these drugs," Kendall added.

He said he did not know which one of the recent ecstasy deaths in B.C. has been associated with PMMA.