Radio New Zealand - Te Reo Irirangi o Aotearoa

An intensive search for a missing Christchurch mother has failed to locate her.

Police say they have grave concerns for Vanessa Picking's safety and spent Wednesday searching a remote reserve on Banks Peninsula for any sign of her.

About 30 officers and search and rescue team members using dogs scoured Godley Head Reserve, about 20km from central Christchurch.

The 27-year-old left her New Brighton home on Monday night with her daughter.

The seven-year-old was found alone in a paddock north of Christchurch on Tuesday morning, but her mother was not with her, nor was a man they had been with.

That man, Malcolm Chaston, also known as Maniapoto Walker, was taken into police custody on Wednesday.

Police had a warrant for Mr Chaston's arrest in relation to a sexual assault on a woman and stopped him near Cheviot in North Canterbury using road spikes.

He will appear in court on Thursday, although police will not say what charges he faces.

The search for Ms Pickering will continue on Thursday and police want to hear from anyone who may have seen her since Monday night.

Ms Pickering has blonde hair and was wearing trousers and a brown jersey.