Police are investigating the death of a 3-year-old boy who was dropped off at University Hospital at Downstate on Sunday by a man and a woman who left before answering any questions. Their relationship to the child is still unknown, according to police sources.

Officials say the boy was unconscious and had visible bruising when he arrived at the hospital shortly before noon. He was pronounced dead a short time later.

Authorities have not yet determined if foul play was involved. The Office of the Chief Medical Examiner will conduct an autopsy to determine the cause of death.

No arrests have been made, and police say the investigation is ongoing.

This is the second suspicious toddler death in Brooklyn within a week. On March 3, a 4-year-old boy was found unresponsive at a family shelter with bruises to his abdomen. His mother and another man were later arrested and charged with child abandonment and drug possession.