Officials leading a crackdown on suspected tax evaders have received documents from UBS with details on which banks its US clients' accounts were transferred to after it was subjected to sanctions, the Handelszeitung newspaper said.
UBS confirmed to the paper that it was ordered by the Swiss financial regulator Finma to deliver the information.
In 2009 the bank became the first to feel the force of Washington's clampdown on tax evasion.
UBS was forced to hand over about 4,000 files of suspected tax cheats and pay a fine of $780 million.
Bern is in the process of negotiating a tax agreement with Washington to address the issue of US nationals hiding money in Swiss accounts.
An ongoing US probe reportedly focuses on 11 Swiss banks, among them Credit Suisse, Julius Bär and Wegelin.