SEOUL (THE KOREA HERALD/ASIA NEWS NETWORK) - Early investigations point to hospital-acquired infections as the possible cause of the mysterious deaths of four newborns at a local hospital in the span of just 80 minutes last week.

A DNA analysis conducted by Ewha Womans University Medical Centre, where the babies died on Saturday (Dec 16) evening while being treated at the neonatal intensive care unit, found an identical type of Citrobacter freundii in three of the four victims.

The hospital suspected contamination of injection tools or IV fluid.

Citrobacter freundii is a bacterium that is common in adults but can cause respiratory, urinary and blood infections in infants.

The Korea Centres for Disease Control and Prevention (KCDC) has also confirmed the finding.

A KCDC official told The Korea Herald that "several people carrying an identical DNA of bacterium means that the infections are highly likely to have occurred in an identical way".

"Prematurely born babies, born between 34 and 37 weeks of pregnancy, have weakened immune systems and are more vulnerable to infections," said a KCDC official, who declined to be named.

Health authorities also suspect that the newborns were infected via contact with medical personnel or through medical appliances.

The four deceased were from the same section of the intensive care unit, where a total of 16 premature babies were in incubators at that time. Three of the four were in the same row and the other was in the next row in a section of the same unit. Each row has three incubators and each section has two rows.

Regarding the hospital's internal investigation results that said injection tools or IV fluid were most likely responsible for the babies' sudden deaths, investigators from Seoul Metropolitan Police Agency said it is "too early to confirm".

Police finished searching the premises of Ewha Womans University Medical Centre around 10.30pm on Tuesday (Dec 19), after eight hours of search and seizure. Potential evidence including incubators, medicators, injection tools and medical records were secured, the police agency said.

Meanwhile, the bereaved families of the four dead babies requested a private meeting with the hospital's officials and staff doctors to call for an urgent investigation and denounce the hospital's lack of hygiene control.

The families have been saying that hospital officials should take responsibility for their negligence.