The four were in incubators at the intensive care unit for infants at Ewha Womans University Medical Center in Mokdong in western Seoul when they died between 9:31 p.m. and 10:53 p.m. on Saturday, police said.
Police said they received a call from the hospital alerting them that four babies were receiving CPR treatment. The four had already died by the time police arrived at the hospital, officials said.
A total of 16 babies were in the ICU at the time. After the deaths, seven were transferred to another hospital and four were to follow suit, with one of them already discharged, officials said. The transferred and discharged babies are in good health.
The bereaved families reportedly said the infants all had bloated bellies and difficulty breathing. Doctors and nurses told police that they had no idea why the babies died.
Police said the National Forensic Service will conduct autopsies on the babies on Monday to determine the exact cause of death. By the Yonhap.