The Mounties say the needles were found in three more potatoes originating from Linkletter Farms in Summerside with the help of metal detection equipment.
The potatoes were returned as part of a voluntary recall and have been sent to a forensic laboratory for more testing.
Police were already investigating seven incidents of potato tampering throughout the Atlantic provinces.
The RCMP say three more pallets of recalled potatoes have yet to be examined.
The potato industry in P.E.I. is offering a reward of up to $50,000 for information on how needles ended up in the potatoes.