Seven people in Kings County landed in intensive care, some with near-fatal respiratory distress, after vaping with cannabis oil pods purchased from un-licensed pop-up vendors.

Six of the seven victims of the black-market vape pods were in their 20s, as SFGate reports, with the seventh being a 60-year-old longtime marijuana user who had just tried vaping for the first time.

Cannabis blog Leafly broke the story, speaking to Kings County Department of Public Health officer Dr. Milton Teske. "If you’re going to vape THC, get it from a licensed dispensary where you know there’s a certain amount of testing required to do," Teske says, noting that customers need to pay the significant upcharge seen at licensed dispensaries in order to ensure the safety of the products.

The exact cause of the seven cases of lung illness has not been determined, but all were linked to illicitly bought vape cartridges.

Per Leafly, these seven California cases appear to be part of a cluster of vape poisonings reported nationwide. The Centers for Disease Control hosted a conference call Monday to discuss the problem, noting a cluster of 15 poisonings in Wisconsin, plus other reports in Nebraska and Illinois. New York State's Department of Health is also investigating a cluster of 11 similar poisonings.

Pulmonologist Dr. Vishnu Bezwada connected the dots with the cases at his hospital in the small California town of Hanford, in Kings County, after seeing multiple cases of acute respiratory distress with severe hypoxia (low oxygen in the blood) in young people in their 20s. Bezwada says he typically only treats one such case per year, usually in an older person. Two of the young people nearly died, but all are now recovering.

As Teske tells Leafly, almost all the California cases mentioned different brand names, but all had bought the cannabis cartridges on the street via word of mouth.

As Leafly explains:

At these markets, vendors sell untested THC products that look similar to tested goods. The empty vape cartridges come in from China. Producers then fill the carts with raw THC oil cut with agents such as propylene glycol, vegetable glycerin, medium-chain triglycerides (MCT) oil, or more exotic chemicals.

The cases all exhibited signs of infection, though disease cultures showed nothing. They all suffered from fluid in their lungs, and hypoxia, and the two worst cases had to be intubated and mechanically ventilated.

Teske says, "Anyone that vapes THC they got off the street and has shortness of breath, tightness in the chest, and trouble breathing — go to the ER and tell them you’re vaping, and have heard about this acute respiratory distress syndrome developing from that."