The United States Border Patrol says a convicted Canadian sex offender drove through a barbed wire fence to cross the international border with two children and their mother.

The border patrol said agents found a cut fence near the Turner Port of Entry between Saskatchewan and Montana, then notified RCMP.

Saskatchewan RCMP issued an Amber Alert on Monday for the seven-year-old girl and eight-year-old boy.

Mounties expressed concern that the children were with Benjamin Martin Moore, 50, who has a history of sexual offences against children and was previously convicted of sexual interference with a minor.

An arrest warrant was issued Tuesday for Moore for failing to report information within seven days of changing his address, which is required for convicted sex offenders.

Later that day, the Amber Alert was extended into South Dakota. Moore was taken into custody at a campground near Sturgis soon after.

The children, as well as their mother, were with Moore.

“I am proud of the work our agents do every day to keep us safe by using their skills as well as interagency relationships to arrest those who have committed crimes in our communities and abroad,” said Richard Fortunato, acting chief patrol agent with U.S. Customs and Border Protection, in a statement Thursday.

U.S. Immigration and Customs Enforcement confirmed that Moore, as well as the mother, remain in custody in Pennington County.

RCMP said it is working with U.S. authorities to co-ordinate Moore’s return to Canada, but no date has been confirmed. No additional charges have been laid but the investigation is ongoing, Mounties said.

The mother has not been charged in Canada, RCMP added.

Mounties said at a news conference Tuesday that Moore was being investigated by social services when he left with the children and their mother.

Officers went last week to their home in Eastend, Sask., to question Moore, but found it abandoned.