SAN SALVADOR, Sept 1 (Reuters) - Salvadoran police on Wednesday briefly detained a digital specialist who is a vocal critic of President Nayib Bukele’s plan to make bitcoin a legal tender, saying they were investigating the computer scientist for financial fraud. The police detained Mario Gomez without an arrest warrant and the cryptocurrency commentator was taken away without being officially arrested, according to Gomez’s lawyer, Otto Flores. He has since been returned to his house. “It is not clear why (Mario) was handcuffed...and was taken away by the police without knowing what he is being accused of,” Flores said, describing the detention as “arbitrary”. There has been a heated debate inside El Salvador about Bukele’s plan to adopt bitcoin as legal tender on Tuesday, making the Central American country the first in the world to do so. El Salvador’s police said on Twitter they were investigating Gomez “for crimes of financial fraud, related to false emails sent to many users of the banking system, where their account statements have been compromised.” Such crimes were on the rise, the police said, without elaborating. Gomez had attended various virtual forums and was active on social media, arguing against the introduction of bitcoin as a tender. Critics say using bitcoin is risky given the cryptocurrency’s volatility and because it could be used to launder money. On social media some touted Gomez’s arrest as another example of Bukele’s government using authoritarian tactics against opponents. Even so, Bukele is hugely popular in opinion polls. The presidency did not immediately respond to a Reuters request for comment. (Reporting by Nelson Renteria, Writing by Drazen Jorgic; Editing by David Gregorio) Our Standards: The Thomson Reuters Trust Principles.