A lawyer representing users in one of four class-action lawsuits against Spain-based crypto trading bot developer Arbistar is calling for authorities to take “forceful” action against its CEO.

According to a report from Spanish news outlet elDiario.es, lawyer Carlos Aránguez said that the response from authorities in regards to Arbistar CEO Santi Fuentes, who allegedly scammed users out of millions, does not match the severity of his crime. Fuentes has been out on probation since his arrest in October for his role in the alleged billion-dollar crypto Ponzi scheme Arbistar ran this year. He was charged with fraud and money laundering.

“We want preventive detention for Santiago Fuentes and for our clients to recover the savings that have been so unjustly plundered,” Aránguez said in Spanish. “It is unacceptable that in the face of a scam like this there hasn’t been a strong reaction on the part of the judicial authorities.”

The lawyer currently represents 130 people out of the reported 32,000 who suffered losses at Arbistar after the firm claimed in September there was an error in the calculations for profits generated by the bot. Aránguez’s clients reportedly lost $4.8 million from the alleged error, and there are at least three other class-action lawsuits against the crypto firm. He said:

“If 130 people have lost four million euros, the overall volume is impressive. We are facing the largest computer scam in our country.”

Aránguez described the scam as “extraordinarily complex and sophisticated,” involving users depositing Bitcoin (BTC) that should have been deposited and sold at a higher price for a profit — hence the name Arbistar, after arbitrage. However, the lawyer said that users never reaped any profits because the bot failed to perform.

Fuentes told Cointelegraph in September that there was no scam or misappropriation of digital assets, and that Arbistar would return the funds in roughly 12 months. He has been released without bail following his arrest in October on charges of fraud and money laundering,