Police are warning drug users after a drug that is 100 times more toxic than fentanyl and 10,000 times more toxic than morphine was found in 10 recent investigations.

The drugs, which were found to contain the powerful opioid carfentanil by Health Canada, were all seized between March 20 and April 8.

That is the same period during which the city saw a spike in overdose deaths, with five people dying over six days from March 30 to April 5.

London Police Chief John Pare said in a press release, “While we can’t say for certain that carfentanil is the cause of these deaths, we need to make sure that those who use substances are aware this is on our streets and that they take the needed precautions.”

Police seized 135 grams of the opioid in the most recent seizures, while prior to that only 60 grams of carfentanil had been seized by London police since 2017.

Carfentanil is normally used as a tranquilizer for very large animals by veterinarians.

Dr. Chris Mackie, medical officer of health of the Middlesex-London Health Unit, said in a statement, "Now, more than ever, people who use these substances need to know that more dangerous and potent poisons are on our streets. When they use, it's critical that they're not alone and that naloxone is close by. "

Free naloxone kits are available through the health unit and local pharmacies.