LONDON, ONT.—Police in London, Ont., say they’ve found the powerful opioid carfentanil in drugs seized in 10 recent investigations.

They say they seized the drugs between March 20 and April 8 — the same period in which five people died of suspected overdoses in the city.

Police Chief John Pare says it is not yet certain that carfentanil caused the deaths, but he is warning users to be aware the opioid is on the city’s streets.

He is asking drug users to carry the antidote naloxone.

Carfentanil is 100 times more toxic than fentanyl.

More than 4,000 Canadians died from opioid overdoses in 2017, the latest full year where data is available.