The teenagers, due to visit their grandparents, were questioned for several hours by US officials who asked them the whereabouts of their father and whether he sometimes worked in the country, according to La Tribune de Genève newspaper.
During their six-hour interrogation the youngsters were not allowed to contact their grandparents who were waiting for them at an undisclosed
airport, the report added.
The development is the latest twist in a long-running tax dispute that has dominated Swiss-US relations in recent years, with Swiss banks agreeing in
April to hand over confidential information to Washington in April so as to avoid US proceedings.
In all, some 10,000 names of people linked to Swiss banks with American clients were given to the US tax office with Bern's blessing, according to
SwissRespect, the organisation founded by Geneva lawyer Douglas Hornung who represents bank employees caught up in the affair.
"I advise my clients not to leave Switzerland," said Hornung, who advises around 40 bank staff in the country.
Another six banks are in Washington's sights – Wegelin, Neue Zürcher Bank, Liechtenstein landesbank LLB and Israeli banks Leumi, Hapoalim and Mizrahi.
Switzerland has signed an agreement on the issue with Germany, Austria and Britain on curbing tax evasion and Swiss President Widmer-Schlumpf recently announced that she hoped to come to a "global solution" on the issue this year.