The Mounties say someone in Labrador City, N.L., found the tampered potato on Sunday.
Police say the consumer bought a bag of potatoes containing the tampered vegetable about two weeks ago, prior to a recall.
Investigators say all of the affected potatoes came from Linkletter Farms, based in Summerside, P.E.I.
The company also supplies the Cavendish Farms plant in New Annan, P.E.I., where sewing needles were detected in french fries on a production run.
The RCMP have said that they believe all of the affected fries were caught before they left the facility.
There have been no injuries.
Linkletter Farms said it immediately notified the Canadian Food Inspection Agency when it discovered the problem two weeks ago and the agency said the company voluntarily withdrew its Link and Market Town brands.
The RCMP have asked consumers in Atlantic Canada to check for metal objects in potatoes supplied by the company and call them if any are discovered.