A woman who drowned in a swollen West Coast river yesterday slipped into the raging torrent after a stop bank gave way.

Photo: Google Maps

The woman was from the Gloriavale Christian Community and was reported missing in the Haupiri River about 8pm last night.

Senior Sergeant Brent Cook said she was walking near the river when the stop bank gave way and she slipped into it.

He said Search and Rescue volunteers and police looked for the woman late into the night.

"[We searched] until it was obvious that it was too dark and the river was too swollen to conduct an inquiry safely. Flooded rivers and streams are quite common so the circumstances and conditions are what we deal with quite consistently over here on the West Coast, however swollen rivers are quite dangerous."

"The conditions are nothing out of the ordinary.

Mr Cook said a member of the public found the woman's body downstream at about 7am and members of Victim Support were now helping her family.

"We'll be offering all the support we can for the family," he said.

Mr Cook said it's unknown how far stream the woman travelled.

He said Police are now acting on behalf of the coroner.