Officials say a Canadian citizen with two minor children was attempting to cross into the U-S at the Peace Bridge on Friday.
However, during the primary examination the officer became concerned the children were not authorized to leave the country when one of them became visibly upset.
After a further inspection, CBP officers discovered the children had been taken from a Toronto sports camp without the custodial parent's knowledge or permission.
The children were returned to their mother while the father was arrested by Toronto police.
No names were released or the ages of the children.