A search and rescue operation is under way in freezing conditions at Lake Tekapo.

Police notified the Coastguard National Operations Centre at about 8pm on Thursday, to a report of a person in the water at the Tekapo River spillway, and Coastguard Mackenzie Lakes volunteers were requested to assist.

A local Coastguard volunteer with his own private vessel, alongside a police officer, began an initial search before the Coastguard Mackenzie Lakes crew arrived.

A Coastguard spokeswoman told Chris Lynch Media the crew was at the scene and actively searching under the lights of a supporting rescue helicopter.

Volunteer rescue personnel at the scene told chrislynchmedia.com they were searching for a person reported missing in the river.

A rescue helicopter had been scouring the river and lake, while a Coastguard rescue boat searched the water and the banks alongside Fire and Emergency crews.

A Fire and Emergency spokesperson said they were called by police to assist the search, but police was the lead agency.