Man at centre of Sask. Amber Alert drove through barbed wire fence in illegal entry: U.S. officials

The two children at the centre of Monday's Amber Alert issued in Saskatchewan remain safe with authorities in South Dakota, but more details are coming out about their journey, including how they, their mother and her common-law partner got across the border.

Their mother and her common-law partner, Benjamin Martin Moore, a convicted sex offender, were arrested in South Dakota on Tuesday at about 11:30 p.m. MT, according to Meade County Sheriff Ron Merwin. Saskatchewan RCMP confirmed on Friday that both are still in police custody.

On Tuesday night, police in Saskatchewan extended the search for the girl, 7, and her brother, 8, into South Dakota following evidence that suggested the group had moved into the U.S. state.

U.S. Customs and Border Protection (CBP) say the group crossed the border illegally into Montana by driving through a barbed wire fence near the Turner port of entry. The agency did not provide any details regarding time or date of border crossing in a news release.

Havre Sector CBP agents patrolling the international border detected a cut fence and informed the RCMP, according to the Thursday release.

"Havre Sector utilized a Border Patrol agent assigned to the Homeland Security Investigations Task Force to assist in locating the man," the CBP said. "Moore was apprehended through multi-agency assistance and co-operation and is currently in custody pending prosecution."

Officers found the group at the Glencoe Camp Resort in the city of Sturgis, S.D., more than 930 kilometres away from their home in Eastend, Sask., according to RCMP.

Merwin said police were fortunate to locate the fugitives because hundreds of thousands of enthusiasts are taking part in the annual Sturgis Motorcycle Rally, many lodging in area campgrounds.

"We all started checking locations where people were staying and checking the campgrounds, and fortunate enough to find one of the campgrounds where they were staying," he said.

Campers say Moore, 50, had identified himself as security at the resort.

"The guy was wearing a security shirt that all the other people who worked the campground security were wearing — exact same attire," William Dukes from Scottsdale, Ariz. told CBC.

The resort posted on social media that its security team had assisted in locating and apprehending Moore, but did not respond to a CBC request for comment.

Brian Lester says he and his wife were surprised to see children on Sunday because they thought it was an adults-only campground.