The B.C. Coroners Service says fentanyl has been detected in more than four out of five illicit drug overdose deaths in British Columbia so far in 2017.

The agency says out of the 876 drug overdose deaths that have occurred in the province from January to July 2017, 706 involved the opioid fentanyl. This is a 143 per cent increase over the number of deaths occurring during the same period in 2016.

"In the majority of the deaths we're investigating, we're seeing fentanyl detected with other drugs. This presents huge challenges for those using illicit drugs and the risk is high," said Chief Coroner Lisa Lapointe. 

In many of the cases, fentanyl was combined with drugs like cocaine, heroin and methamphetamine.

There were 91 suspected drug overdose deaths in July 2017, which represents a 30 per cent increase from last July. The number of drug overdoses so far this year is up 88 per cent from this time in 2016.

The majority of the deaths were concentrated in Vancouver, Victoria and Surrey.

The coroner says while 90 per cent of illicit drug overdose deaths take place inside in private residences or other locations, there were no deaths at supervised consumption or drug overdose prevention sites.