A dog has been safely reunited with her owners after being swept into the Waimakariri River late last night.

Coastguard North Canterbury said their duty officer received a call from police just before 10.

The dog had been swept into the river a few kilometres upstream from the motorway bridge.

The dog was later located on an island in the middle of the river.

Her owner attempted to swim across to retrieve her but was unable to do so because of the strength of the current.

Coastguard North Canterbury said the decision was made not to risk anyone re entering the water at night and the team was asked to assist.

Volunteers responded by vehicle and worked alongside Blackwell Rescue to search the area.

The team searched the north side of the riverbank for several hours without success.

As the crew returned to their meeting point, they located the dog on the stopbank.

Coastguard North Canterbury said the dog appeared frightened but unharmed and was carefully guided back to her owners, who were described as incredibly happy to be reunited.

The organisation said the outcome was a great result for everyone involved and a reminder of how quickly conditions on rivers can change.