Nokia, a Finland-based company recently purchased by Microsoft, was allegedly blackmailed into paying several million euros years ago to hackers who threatened to leak the source code for its smartphone operating system.

The case was first reported by Finnish TV station MTV and has been confirmed by Reuters.

"We are investigating felony blackmail, with Nokia the injured party," Detective Chief Inspector Tero Haapala told Reuters. He declined to give further details.

According to MTV, blackmailers acquired the encryption key for a core component of Nokia's Symbian software six years ago, threatening to leak the source code to the public if the company didn't pay up.

If the source code had been exposed, anyone could have written additional code for the smartphone operating system, including malware. Even Nokia would not have been able to distinguish the extra code from the original, MTV reported.

Nokia officials called the authorities after being threatened by the criminals. They agreed to make the payment in cash, which was left in a parking lot in Tampere, central Finland. The hackers apparently retrieved the cash, but the police weren't able to catch any suspects.

Microsoft recently completed a $7.5 billion acquisition of Nokia. The tech companies had agreed to the deal in September, but the closure was delayed due to pending approvals. The billion-dollar acquisition of Espoo, Finland-based Nokia has been an important step for Microsoft as the tech company looks to grow its Windows mobile phone platform.

"This acquisition will help Microsoft accelerate innovation and market adoption for Windows Phones. In addition, we look forward to introducing the next billion customers to Microsoft services via Nokia mobile phones," Brad Smith, Microsoft general counsel and executive vice president for corporate and legal affairs, said in an official blog post at the time.

See Now: OnePlus 6: How Different Will It Be From OnePlus 5?