An obesity treatment that involves placing balloons inside the patient’s stomach may have resulted in five deaths since 2016, the U.S. Food and Drug Administration said in a new warning. Four of those deaths involved the Orbera Intragastric Balloon System, and one involved the ReShape Integrated Dual Balloon System, the FDA says.

The agency says they don’t know the root cause or the incidence rate of death with these devices, nor have they confirmed that the balloon systems definitely caused the deaths. The five people died with a month of getting the balloons inserted into their bodies, and three of them died within just three days.

The agency is also looking into a couple of additional deaths, one from each of the companies listed above, that may have been a result of complications from the treatment.

“FDA is issuing an update to alert health care providers of five reports of unanticipated deaths that occurred from 2016 to present in patients with liquid-filled intragastric balloon systems used to treat obesity,” the FDA statement reads. “Four reports involve the Orbera Intragastric Balloon System, manufactured by Apollo Endo Surgery, and one report involves the ReShape Integrated Dual Balloon System, manufactured by ReShape Medical Inc.

“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. 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). The Agency has also received two additional reports of deaths in the same time period related to potential complications associated with balloon treatment (one gastric perforation with the Orbera Intragastric Balloon System and one esophageal perforation with the ReShape Integrated Dual Balloon System).”