PRESQUE ISLE – Samples of Prince Edward Island potatoes taken from a truck crossing the U.S.-Canadian border earlier this week were found to contain two diseases that mimic the potato wart fungus, federal agricultural officials said Wednesday.

The truck was hauling one of the first loads trying to cross the border since the fungus was discovered last fall in a field on the island province.

“It looks like something we have to look out for,” Don Flannery, assistant executive director of the Maine Potato Board, said upon hearing about the test results.

The samples were taken from the truck at the Houlton port of entry and sent to the U.S. Department of Agriculture’s research laboratory in Beltsville, Md. Flannery said the potatoes had welts around the eyes on the tuber.

Potato wart causes black cauliflowerlike lesions on the potato. Although not harmful to humans, it renders the potato unmarketable. The fungus can live in the soil for decades, apparently immune to any type of chemical treatment. It also can survive harsh winters.

Meghan Thomas, a spokeswoman for the USDA’s Animal Plant Health Inspection Service, said the Beltsville lab determined that the potatoes were not carrying potato wart. The welts were caused, however, by a combination of two diseases that mimic potato wart, Thomas said.

There was no further information on the type of diseases found or whether they were under quarantine.

Scientists at the Beltsville lab had left for the day and were unavailable for comment.

The shipment was turned back at the border because of soil contamination, Thomas said.

In order to be shipped into the United States, P.E.I. potatoes must be inspected by Canadian officials, washed, treated with sprout inhibitor and packed in containers of 50 pounds or less.

According to Thomas, six loads arrived at the Houlton border crossing Tuesday. Of those, three were cleared by APHIS to proceed and three were rejected for soil contamination.

On Wednesday, four loads arrived at the port of entry. By mid-afternoon, three had been cleared to enter the country.

At least one of the loads exhibited quality problems but was allowed to continue to its destination for a thorough inspection, according to border officials.