MADRID — A disgraced former Spanish banker, Mario Conde, was arrested here on Monday as part of an investigation into whether he fraudulently repatriated the equivalent of nearly $15 million in money he had hidden offshore while presiding over the collapse of one of Spain’s largest banks, Banesto, more than two decades ago.

Mr. Conde was arrested along with six other people, including two of his children and a son-in-law. The arrest was ordered by a judge from Spain’s national court who is inquiring whether Mr. Conde and relatives set up a network of companies to help channel back to Spain money stashed away in offshore accounts in Switzerland, Britain and other financial centers before the demise of Banesto.

Spain’s central bank ousted Mr. Conde and took over Banesto in December 1993 after the lender had accumulated unsustainable losses. Banesto had a financial shortfall of 605 billion Spanish pesetas at the time, equivalent to about $4 billion, and was eventually sold at auction to Banco Santander.

Mr. Conde was convicted on a series of fraud and embezzlement charges and served two separate prison sentences. His arrest on Monday comes as several banking-related corruption cases are moving through the courts, set off by the bursting of Spain’s property bubble in 2008.