The two children found dead in Stoke-on-Trent on Sunday have been named by police as Elizabeth and Ethan John.
A woman was arrested on suspicion of murder after officers were first called to a car wash following reports of a stabbing.
A man in his forties was taken to hospital but has since been discharged.
Officers then went to a home on Flax Street and found two children unresponsive with “significant injuries”.
Despite receiving treatment, both died at the scene.
Ethan was 11 years old and Elizabeth was seven.
Ethan’s school said he was a “wonderful member of our school community” with “impeccable manners and an infectious smile”.
Elizabeth’s school said she was a “ray of sunshine who always had a smile on her face” and was “both bright and popular”.
The 49-year-old woman arrested remains in custody and is being questioned.
Detective Chief Inspector Cheryl Hannan said specially-trained officers were supporting “those closest to the children whilst we find out more about what happened”.
She added: “We are solely focussed on finding out what happened to these two children and supporting those affected by this deeply traumatic incident.”
Anyone who was in the area of Flax Street and Campbell Road between 1.30pm and 2.30pm on Sunday – or who has video from the vicinity – is asked to contact police.
