One of my favorite mysteries.
In 1994 Gloria Ramirez was admitted to the emergency room suffering the effects of cervical cancer. Ramirez was in a state of confusion and experiencing respiratory and cardiac distress. Going into cardiac arrest, workers attempted to defibrillate her heart.
At that point several people saw an oily sheen covering Ramirez’s body, and some noticed a fruity, garlic-like odor that they thought was coming from her mouth. A registered nurse…attempted to draw blood from Ramirez’s arm, and noticed an ammonia like smell coming from the tube. She passed the syringe to Julie Gorchynski, a medical resident who noticed manila-colored particles floating in the blood.
After drawing blood, three staff members treating Ramirez lost consciousness. The emergency room was then ordered evacuated while a skeleton crew stayed behind to treat Ramirez. 45 minutes later, Ramirez was pronounced dead from kidney failure. California Department of Health and Human Services investigated the incident, interviewing all 34 staff. About 10 workers claimed to have been affected, the most serious of which experienced shortness of breath, muscle spasms, and loss of consciousness. All affected workers produced normal blood tests.
One worker spent two weeks in the intensive care unit due to breathing problems, hepatitis, avascular necrosis of the knees, all of which were developed after the incident.
There are many theories as to confirm what happened ranging from the DMSO theory (a chemical used to treat cancer parents) to something as radical as a meth lab.
You can read more here