The new governor of Bangladesh’s central bank, Ahsan Mansur, calculates that about $17 billion was siphoned from the country’s financial system in the 15 years before the government of Sheikh Hasina collapsed in August.

Other economists guess that the true value looted during Ms. Hasina’s rule, before she fled the country, could exceed $30 billion. But no one can say for sure. Using a web of financial schemes, Mr. Mansur said, the perpetrators in the government and at some of the country’s biggest companies pulled off what was effectively the largest bank heist in the history of money. And they did incalculable damage to Bangladesh’s economy.

“The highest level of political authority realized that the banks are the best place to rob,” said Mr. Mansur, an appointee of an interim government in Bangladesh. For an inside job, that meant taking control of the central bank and the ownership of a clutch of private banks and their boards of directors. The banks then issued billions of dollars in loans to companies, some of them fictional, that would never be paid back. Much of that money was then transferred out of the country illegally.