The Food and Drug Administration (FDA) on Thursday issued a safety alert to doctors and hospitals on the so-called Intragastric Balloon Systems, which forgo invasive bariatric surgeries for weight loss by using a balloon that fills up with liquid in the stomach to reduce appetite. These balloons are meant to stay inside the body for six months before deflating and eventually exiting the body the old-fashioned way.

Click here to subscribe to Brainstorm Health Daily, our brand new newsletter about health innovations.

Four of the cases involve Apollo Endo Surgery’s Orbera Intragastric Balloon System while one involves ReShape Medical Inc.’s ReShape Integrated Dual Balloon System. It’s still unclear whether there’s a definitive link between the devices and the deaths.

“All five reports indicate that patient deaths occurred within a month or less of balloon placement. In three reports, death occurred as soon as one to three days after balloon placement,” said the FDA. “At this time, we do not know the root cause or incidence rate of patient death, nor have we been able to definitively attribute the deaths to the devices or the insertion procedures for these devices (e.g., gastric and esophageal perforation, or intestinal obstruction).”

These systems are meant to be alternatives to pricey, and potentially risky, weight loss surgery. They can be put into the body through a simple outpatient procedure. Multiple studies have linked obesity to multiple types of cancer and the epidemic is associated with rises in diabetes and heart diseases.