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 just after 2pm following reports of a stabbing involving a man and a woman.
A man in his 40s was taken to hospital but has since been discharged.
Officers then went to a home on Flax Street and found two children unresponsive and injured inside.
Despite receiving treatment from paramedics 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”.
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Elizabeth’s school said she was a “ray of sunshine who always had a smile on her face” and “both bright and popular”.