Spain's largest bank, Banco Santander offered $1.71 billion Tuesday to reimburse clients who lost money in financier Bernard Madoff's alleged pyramid scheme in the US. Santander, one of the euro zone's largest banks was the hardest hit in the $50 billion scam allegedly run by Madoff. It has said it has total exposure of $3.1 billion in the case, the vast majority of it client money, not its own. It said it was offering the compensation to private customers. It made no mention of institutional investors. The bank said in a statement that it acted with “due diligence” when one of its funds, Optimal Strategic US Equity, commissioned Madoff to handle investments by some Santander clients. The bank says it is offering to give clients back their initial investment, in the form of preferred securities, but not interest accrued through Madoff funds.