Chinese police from multiple cities have arrested three individuals who allegedly stole bitcoins and other cryptocurrencies worth around $87 million.

Chinese news agency Xinhua reported on Saturday that the three were busted on Aug. 15 in the provinces of Hunan and Changchun and the country’s capital Beijing after a months-long investigation launched by the police.

According to the report, a self-declared victim, identified by the surname Zhang, first filed a complaint to the police in the northwestern city of Xi’an in March, alleging his computer had been hacked and crypto assets worth around $14.5 million stolen.

The police investigation, which received assistance from several unnamed internet companies, later located a suspect with the surname Zhou, who they claimed had made a remote attack to transfer the funds from Zhang’s computer.

As the investigation continued, the police further identified two alleged accomplices of Zhou that they said were highly experienced hackers.

The group was further accused of having conducted a series of illegal cyber intrusions into corporate and personal networks to obtain crypto assets initially estimated to amount to 600 million yuan, or about $87 million.

The arrests come at a time when Chinese police are stepping up efforts to crack down on cybercrimes relating to cryptocurrency.

Just a month ago, police in China’s Dalian city also arrested 20 suspects from an IT firm who allegedly used crypto mining malware to infect over a million computers and reportedly earned more than $2 million over two years.