The Metropolitan Police Department has confirmed that a small portion of the approximately 58 billion yen ($533 million) worth of cryptocurrency stolen by hackers has been converted into another digital currency.

The theft of the NEM cryptocurrency from the Tokyo-based Coincheck Inc. exchange has been under investigation by police.

Police officials believe those involved in the theft have begun laundering the stolen funds.

According to investigative sources, confirmation has been made of a so-called dark website that can only be accessed using special software that appears to be providing the opportunity to convert NEM currency into other forms of cryptocurrency.

Police officers have contacted a Japanese male who accessed the dark website and confirmed that he converted a small amount of NEM currency for Litecoin, another cryptocurrency.

The Asahi Shimbun has been conducting an analysis of transactions records for the accounts to which the stolen NEM has been transferred. Since Feb. 7, when Tokyo police confirmed the existence of the dark website, there have been close to 300 transactions between a certain account and a much larger number of other accounts. The total amount of the transactions has exceeded 400 million yen in the NEM cryptocurrency, based on the latest exchange rate.