UPDATE: The Amber Alert has been cancelled. The boy was located Friday morning.

The search for a three-year-old boy from southeast British Columbia has gone international, with authorities on both sides of the border saying they believe the child is in the United States with his father.

Police issued an Amber Alert on Thursday afternoon for Alvin Barnett, who they believe was abducted by his father, 39-year-old Robert Barnett, in the Elk Valley area near Sparwood, B.C., before they crossed the border and into the U.S.

Jennifer Viets, Montana's Amber Alert co-ordinator, said the vehicle the father and son are believed to be travelling in crossed the border near the city of Eureka at around 3 p.m. MT.

"We're pretty worried about the safety of the little boy, so that's why we're using every possible resource to try to find him," she said.

RCMP allege Robert Barnett has abducted his son.

"If anybody sees anything or has any information, they should call 911, especially if they see him. They should not approach the vehicle or the gentleman. We do consider it a dangerous situation."

According to officials on both sides of the border, the pair may be travelling in a 2002 blue Subaru Outback with B.C. licence 347 SBL.

Alvin is three-feet-two-inches tall and 35 pounds, wearing a red shirt and blue jeans, while his father is described as five-foot-five with green eyes, reddish blonde hair and a scar over his right eyebrow.

RCMP spokesman Cpl. Dan Moskaluk said he doesn't know whether or not Barnett holds dual nationality with Canada and the U.S.

"Information was disseminated to our counterparts at the Canadian Border Service Agency and U.S. border crossing points in the Elk Valley area, and at this point in time we do remain in contact with our U.S. law-enforcement counterparts," he said.

Moskaluk said the child and father were together during a supervised parental visit, indicating the father had limited access to his child, and as a result the incident met the criteria for an Amber Alert.

He said he didn't know why the father may have been on a supervised visit.

Viets said as soon as officials in her state were notified of the Amber Alert by the Mounties, the criminal justice system broadcast to all state and local police and sheriffs agencies the information and to be on the lookout for the vehicle, child and suspect.

At the request of the Elk Valley RCMP, officials then issued the Amber Alert, notifying the public and press.

"We have shared out Amber Alert with the state of Idaho and they're re-broadcasting it there," she said. "We've also done a multi-state broadcast to all the western states like Washington, Oregon, Utah, Nevada so that other states are aware of it in case they pass through Montana undetected."

She said Montana is a big state that takes several hours to cross but because Barnett is believed to have crossed in the afternoon it's possible he could have made it into another jurisdiction.

"We're getting tremendous support from law enforcement everywhere, trying to help with this," she said.

Eureka is a small city with a population of about 1,037 people according to the 2010 census, said Viets.

She described the area surrounding Eureka as mountainous, with lots of trees, campgrounds and cabins. It is rough territory, especially if the suspect plans to head off road.

"And we do have snow in that area right now. It's another complication."