UPDATE 1-Germans quiz Credit Suisse clients in tax probe

* German prosecutor's office sends 24 questions

* Credit Suisse clients asked if tax was discussed

* Clients had turned themselves in to German tax authorities

(Recasts and updates with confirmation from prosecutors)

ZURICH, Aug 12 (Reuters) - German authorities have asked around 1,500 German clients of Credit Suisse (CSGN.VX) to provide evidence as part of a probe into whether Switzerland's second-largest bank helped them dodge taxes.

The chief prosecutor's office in the western city of Duesseldorf said in a statement it had written them to ask why they had deposited their money with the Swiss bank.

It confirmed a report by Swiss daily Tages-Anzeiger, which printed a photo of part of the form that listed two questions -- what the clients' account numbers were and why they had chosen to place their funds with a Swiss rather than a German bank.

"The target of the survey is the explanation of the circumstances under which the investments with Credit Suisse came about," the prosecutors said in a statement.

"It should also be determined who participated in the engagements from the bank's side," the office said.

A spokesman for Credit Suisse declined to comment.

TAX EVASION

German tax authorities had passed on names of the Credit Suisse clients after they turned themselves for not paying their taxes in full, the prosecutors said.

The clients had to respond to the questionnaire as they were contacted as witnesses, the prosecutors said.

Searches of Credit Suisse's private banking offices in Germany last month netted huge amounts of data and more than 100 boxes of material after tax authorities obtained a compact disc with names of alleged tax dodgers this year. [ID:nLDE66F1HT]

That was the latest episode in an international crackdown on suspected tax cheats in offshore centres. Last year, Swiss wealth manager UBS (UBSN.VX) (UBS.N) agreed to a hefty settlement after a bitter U.S. tax probe. [ID:nLDE65G0EZ]

The Duesseldorf prosecutor's office sent the Credit Suisse clients 24 questions, Tages-Anzeiger said, including whether there had been any discussion that the funds would not be taxed, whether a courier service transferred funds and whether the possibility of opening two accounts -- with one for untaxed wealth -- had been addressed.

Further clients will probably be questioned as more than 1,500 had turned themselves in to tax authorities, the prosecutor's office said.

"Another possibility is questioning the 1,100 clients whose data is on the CD," the office said. However these people, as suspects, would have the right to refuse to give evidence.

The investigation comes as Germany and Switzerland try to establish a double-taxation accord that could turn up billions of euros of undeclared German cash possibly held in Switzerland.

(Reporting by Catherine Bosley and Sam Cage; additional reporting by Edward Taylor in Frankfurt; Editing by Hans Peters and Michael Shields)