UPDATE 1-Senior UBS employee was detained in U.S. tax probe

(Recasts throughout; adds source identifying executive involved in probe, no comment from U.S. Justice Department and SEC, bylines)

By Katie Reid and Martha Graybow

ZURICH/NEW YORK, May 7 (Reuters) - A senior UBS (UBSN.VX: Quote, Profile, Research) employee was briefly detained by U.S. authorities as part of a probe into whether U.S. clients tried to evade tax obligations with the firm's help, the Swiss bank said on Wednesday.

UBS said the employee was detained under a material witness warrant but declined to identify the person.

"Our understanding is that the respective employee, who has not been charged with any wrongdoing by the U.S. government, will remain in the United States pending discussions with the U.S. authorities regarding resolution of his status as a witness," a spokesman for UBS said in an e-mailed statement.

The U.S. Department of Justice and the Securities and Exchange Commission are investigating UBS's conduct in relation to cross-border services provided by UBS advisers to U.S. clients from 2000 to 2007, UBS said. The bank said it was cooperating with the investigations.

A person briefed on the situation said the detained executive was Martin Liechti, the Zurich-based head of North and South America for UBS's international wealth management business.

An e-mail sent to Liechti by Reuters generated a response that said, "I'm currently traveling with limited access to my e-mail."

The Department of Justice is examining whether U.S. clients tried to evade tax obligations with the help of UBS client advisers, the bank said in its statement.