A fire broke out in a multi-unit residential building in the Gyeonggi provincial city of Ansan early Monday, killing four Nigerian children.

According to fire authorities, the fire erupted on the second floor of the three-story building at around 3:28 a.m. before being extinguished about 40 minutes later.

Four Nigerian siblings, aged between four and eleven, were found dead inside their multiplex unit. Although their parents evacuated with their two-year-old child, they are presumed to have been unable to get all of their children out of the building.

A reported 37 people managed to evacuate, while eleven others were taken to hospitals for smoke inhalation.

Police and fire authorities have launched an investigation into the cause of the fire.