A woman has been arrested on suspicion of murder after three children were found dead in southwest England, police said Sunday.

The Avon and Somerset Police force said officers were called to a house in the Sea Mills area of Bristol shortly after midnight and found the three children inside. It said a 42-year-old woman is in police custody at a hospital.

Neighbors said the children were all under 10, the youngest a baby.

Police did not disclose the relationship between the woman and the children but said it was “an isolated incident.

“This is an incredibly tragic and heart-breaking incident in which three children have sadly died,” said chief inspector Vicks Hayward-Melen.

The force said it had reported itself to the police watchdog because of “prior police contact” with the individuals involved.