A rare fungal infection has killed a California man undergoing cancer treatment and it’s believed he got it from medical marijuana, CBS Los Angeles reports.

The treatment left the man’s immune system compromised, but his death still surprised doctors because he was relatively young and his cancer was beatable. He was using medical marijuana to fend off the treatment’s effects. After his death, testing of 20 medical marijuana samples from across the state found the vast majority were contaminated with dangerous bacteria and fungi.