They are accused of failing to help Spain's police tackle the thousands of protesters who were out in the streets ahead of the October 1 independence referendum.
Secession could also fuel separatist-nationalist divisions across the rest of Spain, which only this year saw ETA guerrillas in the northern Basque region lay down their arms after a campaign lasting nearly half a century.
Yesterday Spain's Constitutional Court suspended a session of the Catalan parliament scheduled for Monday in which local leaders were expected to declare Catalonia's unilateral independence from Spain.
In an interview with Spanish news agency EFE, Prime Minister Rajoy said the solution to the Catalan crisis was a prompt return to legality and "a statement as soon as possible that there will not be a unilateral declaration of independence, because that will also avoid greater evils".
There has been no relaxation in the tension with a strong message from King Felipe VI of Spain accusing Catalan authorities of breaking the Spanish Constitution and their Autonomous Status "in a repeated and systematic manner" and in showing "inadmissible disloyalty to the powers of the state".
On Thursday, Banco Sabadell - one of Catalonia's largest lenders - announced it will move its headquarters from the region as it becomes more likely the Catalan government will declare independence.
However, another regional government official, Raul Romeva, said that the parliament would defy the court ban and go ahead on Monday with a debate that could lead to a declaration of independence from the country.
Spain's government today passed a new law to make it easier for companies to leave Catalonia.
Unlike national police, Catalonia's force, the Mossos d'Esquadra, did not use force to prevent people voting.
Allegedly 90 per cent of the approximately 2.2 million Catalans who voted on Sunday (41 per cent of the total number allowed to vote) casting their vote in favour of separating from Spain.
There was violence at polling stations as police, trying to enforce a Spanish court ban on the vote, attempted to seize ballot boxes and disperse voters. Puigdemont said the results of the vote validated the push to secede.
Elections to the Catalan parliament, which is now led by a coalition of two pro-independence parties - are next due on November 2019.
He was quizzed in Madrid along with Catalan police lieutenant Teresa Laplana, who was questioned by video link from Barcelona due to health reasons; Jordi Sanchez, head of the Catalan National Assembly that has been the main civic group behind the independence movement; and Jordi Cuixart, president of separatist group Omnium Cultural. The Catalan leaders say they want global mediation and have repeatedly urged the European Union to get involved.