Parents of children with autism are turning to a controversial stem cell treatment backed by US Health Secretary Robert F. Kennedy Jr., according to a Guardian investigation published June 17.

A growing number of clinics across the country are charging tens of thousands of dollars for the unproven therapy, which is being administered to children as young as 18 months old, the investigation found.

“‘Autistic kids are being experimented on’: inside America’s booming market for unproven stem cell infusions,” reads the investigation’s headline.

Ed Pilkington, The Guardian’s chief reporter, spent months examining the providers of these treatments and their connections to Kennedy. The investigation found that clinics are marketing stem cell infusions as a potential autism intervention despite a lack of FDA approval or rigorous clinical trials supporting their use for the condition.

Scientists interviewed by The Guardian expressed concern that the FDA may be loosening its restrictions on stem cell treatment for autism, a move that could expand access to unproven therapies for families seeking help for their children.

The investigation was published as part of The Guardian’s “Stateside with Kai and Carter” podcast series.