Police in Japan have identified roughly 30 people for alleged involvement in illegal transactions stemming from 58 billion yen ($530 million at the time) worth of NEM cryptocurrency hacked from the Coincheck exchange three years ago, Nikkei has learned.

The individuals have either been arrested or their cases have been referred to the prosecutors' office, according to a source familiar with the situation.

The 2018 attack on one of Japan's leading cryptocurrency exchanges rattled investors and prompted increased regulatory oversight of the industry.

Conversions involving NEM in these cases total around 20 billion yen, according to the source. The parties responsible for the hack have yet to be identified.

Coincheck's computer system was compromised in a January 2018 cyberattack, with the 58 billion yen in NEM transferred out. The hacked NEM was then offered on the dark web at a 15% discount in exchange for other cryptocurrencies.