The West Coast search and rescue operation has been down following reports that someone is swept down the river that has swell.
A police spokeswoman said the search for the woman had been standing down for the night before 11pm.
"Emergency services were informed that a girl had entered the river at 7.59pm," said the spokesman.
"A search of the area this evening has been unsuccessful. The search will resume in the morning."
Earlier tonight, a spokesman for Greymouth Police said they were responding to reports of a missing person in the river.
"There are emergency services and members of the public at the location and looking for the missing person," they said at the time.
The river runs past the Christian community Gloriavale isolated Western Coast.
The region has been thrown by midnight on Wednesday, which has continued throughout today, often heavy.
Between midnight yesterday and 4pm today, NIWA recorded parts of the West Coast and South Alps receiving over 300mm in hand.
The Ivory Glacier, about 50km as the flight price of Haupiri, received 391mm in hand – more than Clyde, saw Cromwell and Alexandra during the whole year of 2017.
The rain has extended a group of students in a hut in Aspiring National Park and seen students at a West Coast school that had been moved by the police.
In another place, a bridge has dropped in Goat Creek on the State Highway 73 East of Otira following the heavy rain and flood of the area.