Police in Vancouver are warning drug users to be extremely cautious after receiving seven reports of suspected heroin overdoses in the city's Downtown Eastside.

Sgt. Randy Fincham confirmed some of the overdoses took place at Insite, Vancouver's supervised injection site. But police are still advising injection drug users to use Insite because it has medical staff available to help in the event of an overdose.

But a researcher who has studied Vancouver's supervised injection sites says many drug-users avoid Insite and were using a unlicensed peer injection site run by Vancouver Area Network of Drug Users.

Thomas Kerr from with the B.C. Centre for Excellence in HIV/AIDS says many drug-user preferred the unapproved VANDU facility because because they need assistance injecting.    

"We know that many drug users actually require manual assistance with their injections, and those individuals are much more likely to acquire HIV infection and they're much more likely to overdose," says Kerr.

But the Vancouver Coastal Health authority served VANDU with a cease and desist order and it was shut down in February, according to reports.

Kerr says under federal law, Insite's staff is not allowed to supervise assisted injections of illegal drugs.  

As the only legal supervised injection site in North America, Insite has seen more than two million visitors since it opened in 2003 and not a single death.

Police urge anyone seeing someone appearing to be in medical distress to call 911. Drug users who don’t feel well after injecting are urged to seek medical attention or help immediately.