A 27-year-old woman has been arrested by officers from the Police Service of Northern Ireland (PSNI) serious crime branch and is in custody after police launched a murder investigation into a boy (3).
Earlier, today police launched a murder investigation into the death of a three-year-old boy in July.
The PSNI said the boy was found dead in Lisburn, Co Antrim, on July 4.
A spokeswoman said: "Detectives are now treating this as a murder investigation.
"The woman remains in custody at this stage, helping police with their inquiries. There are no further details available."
The boy was found at Trinity Terrace, close to the centre of the city.
According to the Belfast Telegraph, neighbours said residents of the newly refurbished terrace, located behind a Domino's pizza takeaway and near Holy Trinity Nursery School, had moved into the busy side street just a few months before the death.