Doral Financial, the troubled Puerto Rico bank that was once a darling of Wall Street before becoming known as a political pariah on the island, has been shut down by banking regulators.

The Federal Deposit Insurance Corp. expects to lose about $748.9 million from Doral’s collapse, making it the most costly bank failure since April 2010, when another Puerto Rican bank collapsed.

The takeover of Doral on Friday was marred by the FDIC’s early release of an emailed announcement that the bank had been shuttered. The email was sent hours before many of the bank’s branches had closed and while Doral’s stock was still trading on the New York Stock Exchange.

The release sent Doral’s shares, which had already been hammered in recent months, down more than 46 percent, although it appeared not to rattle customers at the bank’s main headquarters in San Juan.

An FDIC spokeswoman said the email was sent to reporters “in error” but declined to say why it happened.

The collapse of Doral, which over the years weathered a devastating fraud and more recently was ensnared in a murder investigation into the shooting of a top bank executive, seemed all but inevitable.

Like many banks in Puerto Rico, Doral has struggled amid the island’s deep recession and high unemployment.

For months, the bank had been battling with the Puerto Rico government over a $239 million tax refund that Doral executives were counting on as a significant source of capital. Earlier in the week, a Puerto Rico appeals court ruled that the bank was not entitled to the refund — a ruling that appeared to seal the bank’s fate.

Faced with repeated warnings from regulators that the bank didn’t have enough capital, Doral has been selling off assets in recent months, but those sales fell short of saving the bank from collapse.

On Friday, federal banking officials fanned out across Doral’s offices in Puerto Rico, Florida and New York and began transferring $4.1 billion of customer deposits over to Banco Popular.