A search and rescue operation on the West Coast has been stood down following reports of a person being swept down the swollen Haupiri River.

A police spokesperson said the search for the woman had been stood down for the night shortly before 11pm.

"Emergency services were notified that a woman had gone into the river at 7.59pm," the spokesperson said.

"A search of the area this evening has been unsuccessful. The search will resume in the morning."

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Earlier tonight, a spokesperson for Greymouth Police said they were responding to reports of a person missing in the river.

"Emergency services and members of the public are at the scene and are searching for the missing person," they said at the time.

The river runs past the isolated West Coast Christian community Gloriavale.

The region has been drenched by rain from about midnight on Wednesday, which has continued throughout today, often heavily.

Between midday yesterday and 4pm today, NIWA recorded parts of the West Coast and the Southern Alps receiving over 300mm of rain.

The Ivory Glacier, around 50km as the crow flies from Haupiri, received 391mm of rain - more than Clyde, Cromwell and Alexandra saw in the entire year of 2017.

The rain has stranded a group of students in a hut at Mt Aspiring National Park and saw students at a West Coast school evacuated by police.

Elsewhere, a bridge has collapsed at Goat Creek on State Highway 73 east of Otira following heavy rain and flooding of the area.