Artur K. faced charges including membership of an organised crime group, aiding the misappropriation of customer funds and money laundering.
A decision on pre-trial custody will follow his questioning, Anna Adamiak, spokeswoman for Poland's prosecutor-general, told reporters.
The former police officer was detained as part of an investigation into alleged large-scale fraud at Zondacrypto and the unresolved disappearance of Sylwester Suszek.
Suszek was the founder and first owner of BitBay, Zondacrypto's predecessor, who went missing in March 2022.
A search of Artur K.'s home uncovered documents related to Zondacrypto's operations, authorities said.
Investigators are separately searching a fuel depot where Suszek was last seen before he disappeared, using specialist forensic equipment.
The investigation into Zondacrypto was launched in April by regional prosecutors in the southern city of Katowice over allegations of large-scale fraud and money laundering, after several thousand complaints were filed.
In August, it was merged with a separate investigation into Suszek's disappearance.
The case has already led to the detention of Radosław Piesiewicz, former head of the Polish Olympic Committee (PKOl).
(ał/gs)
Source: PAP, interia.pl