Milwaukee officials say they responded to five probable overdose deaths in the Milwaukee area in just one day.
It happened on Saturday.
Officials say when they usually see a spike in deaths like this, toxicology testing will identify if fentanyl or a new type of drug is the culprit.
Authorities say it's possible the drug user is unaware that the fentanyl was added or substituted into the heroin supply. To help combat the problem, one local pharmacy is offering drug drop-offs at all 10 of their locations.