UPDATE 6.48AM: The search has resumed for a woman believed to have drowned at the river mouth at the Hawke's Bay town of Haumoana.

Detective Senior Sergeant Martin James said it appeared the woman had disappeared while trying to help one of two children with her at the beach.

A rahui has been put in place at the beach and it won't be lifted until the woman is found.

The children made it back to the beach, but not their mother.

A significant effort was made by rescue services to find the woman before dark, but it had been unsuccessful and the search ended.

The police dive squad was due to arrive in Hawke's Bay this morning with the search getting underway at first light.

James confirmed the woman was the mother of "at least one the children", who were reported to be two girls aged 5 and 8. The children were treated in hospital overnight.

"We understand the woman had two children on [the inlet point]. One got into difficulty, and the woman has gone in to assist the child.

"It appears she has gone under and hasn't come back up."

He said although two children had been taken to hospital in a stable condition, it was thought that only one had been in trouble.

Both made it back on shore, however the woman remains missing.

"Police would like to thank the volunteers and those who assisted with this 
evening's search, including the Fire Service, Hawke's Bay Rescue Helicopter, 
Coastguard, and Surf Lifesaving."

Emergency services are still looking for the woman. (Photo \ Warren Buckland)

 

Searchers in the water. (Photo \ Warren Buckland)

Hastings resident George Araia was one of the last to see the missing woman. 

He had been fishing with a friend at the confluence of the river and beach all day.

From his spot he had seen the two children playing. He believed the missing woman had walked across the beach past him and his fishing companion.

"We saw her walking toward her grandchildren. Nothing seemed strange."

Police would not confirm the age of the woman or whether she was related to the children hospitalised.

Araia spent the afternoon helping in the search for the missing woman. He said the two children had been found about half an hour apart.

A Haumoana resident, who saw the family just before the incident, said they appeared to be playing, and nothing seemed to be wrong.

He said in the space of ten minutes between him leaving to speak with some friends and returning, the two children had gotten into trouble. He did not see the woman.

He watched emergency services bring two children to shore, who he thought were around the ages of 7 and 12.

Police waders are scouring the mouth of the Tukituki River, which lets out near the beach.

A St John Ambulance spokeswoman said they were called just before 5pm to a water incident on Domain Road, Haumoana.

"We sent one ambulance and transported two patients with moderate injuries to Hawke's Bay Hospital."

They could not provide the patients' names or genders.

The search is being co-ordinated by police, and involves other emergency services, Coastguard, surf lifesaving, and a helicopter.