A 19-year-old Calgary man has been charged with abduction after police say he snatched his eight-year-old half-sister, nearly prompting an Amber Alert before police found the pair driving west through British Columbia.

Family members called police around 5:30 a.m. Wednesday when they realized the girl's brother and a vehicle were missing from their home in Greenview in the city's northeast.

Police determined the two were driving to British Columbia and alerted RCMP in that province.

Officers spotted the car near Hope, B.C., and stopped it near Abbotsford.

The girl was unharmed and her father flew to B.C. to be reunited with her through a Missing Children Society of Canada and WestJet program, police said.

"We're still not sure what his motive was for taking his sister," Staff Sgt. Rob Davidson of the Calgary Police Service's domestic conflict unit.

"It was very challenging to figure out what exactly was going on."

The teen will be returned to Alberta later this week and will be interviewed by investigators. He could face more charges related to the incident, Davidson said.

No weapons were found in the vehicle the teen was driving when it was stopped, but the brother and sister had their passports with them, the officer said.

The girl was located just as police had determined the incident met the four criteria for an Amber Alert — that the victim has been abducted, that they face imminent risk, that the public could have helpful information, and that it happened recently.

Davidson said the accused was not previously known to police and that there is no history of domestic conflict or violence in the home where the brother and sister lived with their mother, father and at least one other sibling.

Police said no names would be released because the victim is a minor.