A nutritional supplement that was given to four premature babies who abruptly died in a South Korean hospital last month has been found by the U.S. to pose health risks to preemies.

The U.S. Food and Drug Administration is notifying through its Web site that it received reports in the past regarding deaths of premature babies associated with SMOFlipid. 

The agency warns that the effects and safety of the intravenous fat emulsion have not been proven for premature infants, noting the dead babies in the reported cases had accumulated fat in their lungs. 

The South Korean public became aware of this after local authorities concluded on Friday that bacteria called Citrobacter freundii caused the sudden deaths of the four infants last month at Ewha Womans University Mokdong Hospital.

The Ministry of Food and Drug Safety dismissed the possibility that they died because of SMOFlipid, as autopsies by the National Forensic Service showed no accumulated fat in their lungs. 

The ministry said no adverse effects of SMOFlipid have been reported over the past ten years or so, adding there is no ground to see it as the cause of the deaths.