VANCOUVER -- A drug-checking program has found that more than 60 per cent of the substances tested at two supervised consumption sites in Vancouver didn't contain any of the drug that people had expected.

Dr. Ken Tupper with the B.C. Centre on Substance Use says the findings were particularly stark when people brought in what they thought was heroin but 88 per cent of it tested positive for fentanyl.

The BC Coroners Service has said the illicit opioid fentanyl was detected in about 83 per cent of the over 1,400 overdose deaths last year in the province.

In a bid to stem the overdose rate, the drug-checking program was launched last November, using fentanyl test strips and a portable machine that tests small samples of illicit drugs for contaminants.

The first six months of the program saw 1,714 samples tested and the centre says 61 per cent of those samples did not contain the drug the user expected.

Tupper says the program is anonymous, so researchers haven't been able to study if people change their behaviour as a result of the tests.