Cecilio Vadillo, a representative of the Interior Ministry in the northern Castilla-Leon region, said the children were found Monday morning after police were summoned to the home in the town of Boecillo.
He said police found the three special-needs children and a 55-year-old woman who worked at the home with cuts to the head and wrist that could be consistent with a suicide attempt.
Vadillo said she is in custody at a hospital but has not been arrested, and the cause of the children's death is under investigation. The newspaper El Pais quoted investigators as saying they were suffocated.