BISMARCK, N.D. (AP) -- North Dakota officials are urging anyone who spots a wild pig to report it immediately, after recent sightings in neighboring states.

Wild pigs -- also known as feral swine -- can carry diseases that threaten domestic pigs and other livestock, State Veterinarian Susan Keller said. They also compete with native wildlife for food and destroy habitat, according to Jeb Williams, assistant wildlife chief for the state Game and Fish Department.

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Wild pigs have been found in the southern U.S. for years, and have been extending their range north and west, now numbering more than 5 million in at least 39 states, Keller said. They are occasionally reported in North Dakota.

"We are asking farmers, ranchers, hunters, hikers, campers and others to report any sightings of feral swine," Keller said in a statement.

One was spotted near the northeastern South Dakota town of Britton in late October.

Kyle Siebels and Cody Packard were helping a farmer harvest corn when a wild pig ran out of the cornfield. They killed it with four bullets from a deer rifle, then reported it to Marshall County conservation officer Casey Dowler.

"I didn't really even know what to think," Dowler told the American News. "I just thought, 'That's one of the strangest calls I've had as a game warden in South Dakota.'"

"They're bad news," he said of wild pigs. "We don't want these animals in South Dakota, any way, shape or form."