Police in the Halifax area say they've identified the party drug that made several people sick since last weekend.

Several people between the ages of 17 and 25 wound up in hospital last weekend after taking what they thought was ecstasy. Some were there for days, and a representative for the Capital District Health Authority said one person was treated in the intensive care unit.

RCMP said Friday that a drug analysis revealed the tablets were actually a substance called Foxy, also known as psychedelic tryptamine.

Unlike ecstasy, psychedelic tryptamine can cause hallucinations, vomiting, nausea and paranoia. Police said the drug has been associated with two deaths in the U.S. due to kidney failure.

RCMP Const. Craig Foley, who is with the RCMP's synthetic drug unit, said said many tablets that are presented as ecstasy are only pure about 25 per cent of time when they are tested by Health Canada.

"We as police, the people on the streets and even the traffickers don't have any idea what is in these tablets," he told CBC News.

"You can usually speculate, but until we actually get our Health Canada analysis results back, we don't know what's in these tablets."

Earlier on Friday, Dalhousie University sent an email to its 16,000 students, warning them of the pills.

"This is not someone vomiting up a bad experience," said Mike Burns, the director of security services for Dalhousie University.

"Young people in the hospital, been there for a couple of days, and you start to worry about things."

In 2009, RCMP said ecstasy was as popular among teens and young adults in Nova Scotia as marijuana, but cautioned that many tablets were mislabelled.

Nearly 60 per cent of the tablets sent for testing were a mixture of other substances, making the drugs more addictive and dangerous, RCMP said.