PRESQUE ISLE — State agriculture officials were crying foul Tuesday after Canadian officials claimed some Maine seed potatoes shipped into New Brunswick were infected with a viroid that affects the potatoes’ shape.

A viroid is the smallest-known part of a virus.

Subsequent testing to date on the American side has shown no evidence of any diseased material in the potatoes in question, according to state officials.

“At this point, nobody even knows what it is,” that was found in a shipment of seed potatoes from a single source in southern Aroostook County, said Terry Bourgoin, director of plant industry for the Maine Department of Agriculture.

The incident appears to be isolated and poses no threat to the potato industry on either side of the border, Bourgoin said.

According to Canadian press reports, federal inspectors inpounded the shipment destined for about a dozen farms in New Brunswick. The “spindle tuber” viroid was discovered during a routine inspection conducted when potatoes cross the border.

Bourgoin said the Shepody variety of seed potatoes was shipped in early May from an unidentified southern Aroostook County grower. Shepody is a long white variety used in processing.

When a report was made to Maine officials, they expressed doubt since spindle tuber is a rare disease in Maine’s modern-day potato industry. The viroid essentially has been eradicated through tissue testing at the state’s seed production farm in Masardis, Bourgoin said.

Spindle tuber viroid causes the potato to become pointed on the end, making it less marketable because of its appearance.

A sample of 8,000 tubers from the southern Aroostook farm was sent to a private testing firm in Indiana. Also, the three tubers found by Canadian testing to contain the mysterious viroid were forwarded to the independent firm for testing.

Using a test developed specifically to detect the spindle tuber viroid, the Indiana firm found no evidence of the viroid in the entire sample, including the suspect potatoes tested in Canada, according to Bourgoin.

At the same time, Maine officials asked Dr. Robert Owens, a USDA plant pathologist and a viroid expert, to conduct testing. Samples were gathered from the storage facility where the seed potatoes were kept. About 60 tubers were sent, Bourgoin said.

Owens is using the same test used by the Canadians on the seed potatoes. To date, Owens has tested one-third of the sample, finding no evidence of the spindle tuber viroid, Bourgoin said.

The test used by the Canadians and Owens is less specific than the procedure used by the Indiana testing facility, according to Bourgoin.

Maine’s agriculture commissioner, Ed McLaughlin, plans to fax a letter to his counterpart in New Brunswick today saying no statements should have been made until a specific determination was made regarding the viroid.

“The (news) papers are playing it up as a disease,” the commissioner said during a visit to Presque Isle. “Neither side knows what’s going on.”

Efforts to contact federal and provincial agriculture officials late Tuesday afternoon were unsuccessful. A spokesman for the New Brunswick Potato Agency said there is no concern about the viroid found in the Maine potatoes.

The seed was detained and not allowed to be planted, which was good for the industry on both sides of the border, said Patton McDonald of the potato agency.