The royal family has tried mightily to distance itself from the investigation. Officially, the palace has insisted that the king knew nothing about the foundation activities of Mr. Urdangarin, who has pledged to prove his innocence. It publicly maintains that Juan Carlos ordered his son-in-law to abandon the troubled foundation in 2006, a year before dubious financial dealings surfaced.

But last weekend, the duke’s former business partner, Diego Torres, who is also under investigation, told a judge that the duke made no move without palace approval, and he turned over nearly 200 e-mails to support his claim. Many of those e-mails have now surfaced in the Spanish news media. Others were provided to The New York Times by a person close to the legal process who did not want to be identified for fear of retribution.

The e-mails suggest that the palace was concerned about what was going on at the sports charity well before it has acknowledged, and began pressuring Mr. Urdangarin to leave it at a time when investigators now say he and his partner were involved in inflating contracts and moving money offshore. Despite the palace’s insistence that the king had little to do with his son-in-law, the e-mails show that the king was monitoring his affairs. They include boasts by Mr. Urdangarin about the king’s backing of sponsorships for events he was organizing.

The e-mails do not indicate any wrongdoing by the king. But they have brought the scandal to the palace doorstep, further tarnishing a monarchy that has come under scrutiny as Spaniards suffer through an economic downturn and as corruption cases — including envelopes of cash handed out to top politicians — stoke their resentment over the privileges and special connections that have insulated Spain’s elite from the same pain.