Spanish police arrested Catalonia’s junior economy minister Josep Maria Jove on Wednesday as part of a raid on regional government offices ahead of an unauthorized referendum on independence, sources within the Catalan government said.

Axar.az reports citing Reuters that, Spanish police entered offices of the Catalan region’s economy, interior, foreign affairs, welfare, telecommunications and tax departments, the sources said.

Tensions with Madrid have ramped up in the last few weeks as leaders in the wealthy northeastern region vow to go ahead with an Oct. 1 vote on splitting from Spain which the central government says is illegal and cannot take place.

El Pais newspaper said 14 people in total had been arrested.

On Tuesday, Spain’s Civil Guard, a national police force, seized over 45,000 envelopes packed in cardboard boxes that the Catalan government was ready to send to notify people around the region about the referendum.

The first of hundreds of Catalan mayors were also forced to appear before the state prosecutor on Tuesday after they said they would back the referendum.