A person in Lower Hutt, where two young siblings were severely injured, has come forward to police. 

Two Lower Hutt children, aged four and five, were hospitalised with "very, very severe" injuries believed to have been inflicted deliberately over "a long period of time", police said on Friday. 

One had "brain bleeds and severe internal injuries". 

Detective Senior Sergeant Rebecca Cotton says the information the person had provided would help police enquiries. 

No arrests have been made and no charges had been laid, police said. 

The investigation into how the children's injuries were sustained was progressing, she said, but police continued to have "varying degrees of engagement" from the family. 

Cotton said the siblings are recovering well since they were discharged from hospital. 

The police continue to appeal for witnesses to come forward. 

Police said the children's family had recently moved to Stokes Valley and had been in their new home just two nights when they were hospitalised. 

They were known to both Oranga Tamariki and police, who had visited the home previously. 

Kainga Ora said the case was not related to any of its houses.