"They were detained. Each of them was presented with a European arrest warrant in the presence of lawyers. In accordance with the procedure, the Brussels Prosecutor's Office then requested an investigator to execute European arrest warrants", the prosecutor's office said in a statement.
The prosecution added that Comin and Puig did not agree to their extradition to Spain, while the hearings in their case were scheduled for 15 November.
"Puig and Comin did not give their consent to extradition to Spain. An investigator decided to release them provided that they cannot leave the country and must stay in touch under any circumstances", the statement noted.
The statement comes after former Catalan Minister of Health Antoni Comin and former Minister of Culture Lluis Puig voluntarily appeared on 7 November before Belgium's police for questioning.
Hearings on the extradition of former Catalan President Carles Puigdemont, who faces European and international arrest warrants, are scheduled for 16 December.
Twelve of his compatriots in the pro-independence movement were sentenced on 14 October for their involvement in the illegal referendum two years prior. Nine were found guilty of rebellion and received sentences ranging from 9 to 13 years in prison. The remaining three were sentenced for the lesser crime of disobedience. This triggered protests and riots across the autonomous community.