The vote on breaking away from Spain, planned for 1 October, has been suspended by the constitutional court.
As a result, the Public Prosecutor’s Office instructed security forces to take everything which could help with the “consummation of the crime”.
This includes promotional materials and the ballots themselves, Spanish newspaper El Pais reports [in Spanish].
The order came as Spanish tennis champion Rafael Nadal came out strongly against the plans.
“You can’t skip the laws because you want to skip them,” Nadal told a paper.
The referendum, which was approved in the separatist-dominated regional parliament, has been suspended by Spain‘s constitutional court but Catalan leaders have vowed to hold it regardless.
In his speech in June, Guardiola appealed to the international community and “democrats the world over” to support Catalans’ “right of freedom of expression and the right to vote”.
Barcelona saw a massive outpouring of support for independence on Monday when Catalans marked their national day, the Diada, with marches and rallies.