NEW YORK (Reuters) – U.S. prosecutors are building potential cases that would accuse North Korea of directing the theft of $81 million from Bangladesh Bank’s account at the Federal Reserve Bank of New York last year, and that would charge alleged Chinese middlemen, the Wall Street Journal reported on Wednesday.

The U.S. Federal Bureau of Investigation believes that North Korea is responsible for the heist, an official briefed on the probe told Reuters. Richard Ledgett, deputy director of the U.S. National Security Agency, publicly suggested on Tuesday that North Korea may be linked to the incident, while private firms have long pointed the finger at the reclusive state.

The Journal, citing people familiar with the matter, reported that prosecutors believe Chinese middlemen helped North Korea orchestrate the theft from Bangladesh’s central bank, which was among the biggest bank robberies in modern times.

The current cases being pursued may not include charges against North Korean officials, but would likely implicate the country, the newspaper reported, with the United States accusing a foreign government of orchestrating the heist.

A U.S. Department of Justice spokesman declined to comment.

FBI offices in Los Angeles and New York have been leading an international investigation into the February 2016 incident, in which hackers breached Bangladesh Bank’s systems and used the SWIFT messaging network to request nearly $1 billion from its account at the New York Fed.

The branch of the U.S. central bank rejected most of the requests but filled some of them, resulting in $81 million disappearing into casinos and other entities in the Philippines. A top police investigator in Dhaka told Reuters in December that some Bangladesh Bank officials deliberately exposed its computer systems, enabling the hackers to get in.

The incident exposed bungling and miscommunication between central banks, and left the Fed, Bangladesh, SWIFT, and the Philippine lender that initially received the funds trading blame for months.

SWIFT – or the Society for Worldwide Interbank Financial Telecommunication that serves as the backbone of global finance – has since revealed that its messaging system has been targeted in a “meaningful” number of other attacks last year using a similar approach as in the Bangladesh incident.

Last week, SWIFT said it planned to cut off the remaining North Korean banks still connected to its system as concerns about the country’s nuclear program and missile tests grow.

The Journal reported that federal investigators are focusing on Chinese individuals or businesses who allegedly helped North Korea orchestrate the heist, and that the U.S. Treasury is considering sanctions against these alleged middlemen.

The New York Fed and SWIFT declined to comment.

(Reporting by Jonathan Spicer and Joseph Menn; Editing by Jonathan Oatis and James Dalgleish)