Five people who were using an obesity treatment that places balloons inside their stomachs have died since 2016, according to the US Food and Drug Administration.
Four of the deaths involved people using the Orbera Intragastric Balloon System and one involved ReShape Integrated Dual Balloon System, the agency said.
"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," the FDA said in a safety alert issued Thursday.
The five people died within a month or less of having the balloons inserted.
Three died one to three days after the balloon placement. The remaining two deaths could be related to "potential complications associated with balloon treatment," -- one was a stomach perforation and the other was a perforation in the esophagus, according to the FDA.
The process involves placing one or two uninflated balloons using an endoscope that goes through a patient's mouth into the stomach. Then saline is used to fill the balloons. The inflated balloons stay there for six months, taking up space inside the stomach so the person feels full.
The FDA said it's working with both companies, Apollo Endo-Surgery and ReShape Medical Inc., to understand the deaths and "to monitor the potential complications of acute pancreatitis and spontaneous over-inflation."
In February, the agency had recommended that health care providers monitor patients who got the balloons for acute pancreatitis and spontaneous overinflation.
According to Apollo Endo-Surgery, there has been one additional death of a person who received its device. In a press release, the company said it self-reported one death each in the US, Great Britain and Mexico and two in Brazil.
The company said it "received no product liability-related claims in connection with these five cases" and noted that the incidence rate "remains less than 0.01%," which is in line with what it reports in the directions for use of the device. It states that of more than 277,000 devices distributed, there have been 21 reported deaths from January 1, 2006, through March 31, 2017.
"The FDA's letter to Health Care Providers does not indicate that the patient deaths were related to the ORBERA device or the insertion procedures. While the cause of death has not been provided or determined in all cases, Apollo has not received any communication or indication from the attending physicians or hospitals that the deaths have been due to the ORBERA device," the company said.
In a statement emailed to CNN, ReShape Medical said, "There is no responsibility that we take more seriously than patient safety. ReShape is committed to supporting the continued safe and effective use of the dual balloon and is proactively communicating with physicians about this FDA update. Patients with questions about this FDA update should contact their physicians directly."