West Yorkshire Police launched a murder investigation after the bodies of Wheldon Infant School teacher Sarah Laycock, 31, and her eight-year-old daughter Abigail Miller were discovered at their home on Kirkby Avenue, Garforth, on Saturday January 14.
A police spokesman said the 36-year-old man arrested on suspicion of murder and attempted murder had now been moved to secure psychiatric accommodation after receiving hospital treatment.
Police discovered the bodies after being called to reports of an assault at Fairburn Ings nature reserve, near Castleford, at around 4pm on Saturday.
A four-year-old girl, understood to be Miss Laycock’s youngest daughter Omelia, was found with minor injuries at the house but has since been discharged from hospital.
Police inquiries are continuing.
Witnesses or anyone with information should contact police on new non-emergency number 101 or Crimestoppers, in confidence, on 0800 555111.