Bangladesh's central bank became more vulnerable to hackers when technicians from SWIFT, the global financial network, connected a new bank transaction system to SWIFT messaging three months before a $81 million cyberheist, Bangladeshi police and a bank official alleged.

The technicians introduced the vulnerabilities when they connected SWIFT to Bangladesh's first real-time gross settlement (RTGS) system, said Mohammad Shah Alam, the head of the criminal investigation department of the Bangladesh police who is leading the probe into one of the biggest cyberheists in the world.

"We found a lot of loopholes," Alam said in an interview in Dhaka. "The changes caused much more risk for Bangladesh Bank."