The investigation follows a complaint from the copyright protection arm of Spain's authors and publishers association. It said it had detected evidence of a large-scale operation to scan original works.
A police statement Sunday said investigators turned up eight large-capacity photocopying facilities in Madrid and Seville where works by prestigious authors were being copied "massively."
It didn't say when the arrests happened or how much the books were worth in total. But it said over 1,000 published books and 10 computer hard discs full of texts for publishing were seized.
The statement said a Spanish police unit focusing on Asian organized crime was involved, though it did not elaborate.