The San Diego County Sheriff's Department issued a warning Thursday to avoid a counterfeit street drug believed to be the cause of multiple deaths over the last 24 hours.

Deputies say the pills are known as "Blues" or "M 30's" and are known to contain fentanyl or carfentanyl, a synthetic opioid lethal in even the smallest dose (2 micrograms). They are counterfeit Oxycodone.

Investigators aren't yet sure what are in these counterfeits, but SDSO Undersheriff Michael Barnett said that deputies responded to four fatal overdoses believed to be linked to them in the last 24 hours. Those overdoses occurred in Poway, Santee, Lakeside and Valley Center.

Investigators are unaware how many pills the victims took. Barnett said they are following up on the source of the supply.

According to Barnett, it's logical to assume there is a common source of supply somewhere up the supply chain.

Safety Alert: We believe this counterfeit blue pill has been the cause of several deaths in the county in the last 36 hours. We urge you not to take this unsafe drug. Dealers promise a painkiller high, but no one knows what exactly is in the drug which makes it so dangerous. pic.twitter.com/qq69ONaq8Z — San Diego Sheriff (@SDSheriff) July 25, 2019

The pills are blue and round and have the letter M inside a square on one side and the number 30 on the other. They can be taken orally or they can be crushed and smoked, according to Barnett.

The pills are advertised as having a "painkiller high." Investigators are still trying to determine how many calls for service they've responded to in connection with the pills in the last 24 hours.

Barnett said the counterfeit pills are typically made with pill presses at someone's home. Pill presses are widely available -- the DEA says a $1,000 investment for a press and a mold, and a few thousand more for materials can produce between $5 and $20 million in sellable, perfect looking pills with deadly consequences.

According to Barnett, there were 273 unintentional prescription overdoses in the county in 2017 and 253 in 2016.

Deputies have administered 123 successful doses of Naloxone -- an emergency narcotic overdose antidote -- in the last five years, Barnett said.

Anyone with information is urged to call the Crime Stoppers anonymous tip line at (888) 580-8477.

Anyone struggling with a drug or alcohol addiction can call the County Crisis Hotline at (888) 724-7240.

The SDSO allows people to dispose of unwanted or expired prescription drugs at drop-off sites throughout the county. More information can be found here.

No other information was available.

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