As probe continues into the February Bangladesh Bank cyber heist, more details are coming to light including a new report that the US Federal Reserve Bank had reportedly blocked four requests for transfer of $81 million hours before then approving them.

Officials close to the investigations told Reuters that the US Fed had first turned down 35 money transfer requests via SWIFT on the grounds that they did not have the required formatting, but when the hackers resubmitted them, four of these, totaling $81 million, went through. One was rejected because of spelling error, and 30 were put on hold for sanction review and later found to be fraudulent.

While the Fed has held Bangladesh Bank and SWIFT responsible for allowing the messages to get through, officials at Bangladesh’s central bank have questioned the Fed’s failure to see the red flags, says Reuters.

The US House Science Committee has launched a probe into Fed’s handling of transfers while SWIFT says it is planning an improved security program.

The wired-out money remains untraceable.

Read full story at Reuters.