BEIJING - Local authorities in Central China's Henan province have raided a publishing house suspected of printing pirated books and found some 20,000 illegal copies, China's publication watchdog announced on Monday.

According to the National Office Against Pornographic and Illegal Publications (NOAPIP), they informed local authorities about the case after being tipped off by a letter in November.

Local law enforcers in Zhoukou city then raided Longtu Printing Company and confiscated the illegal publications, most of which were driving test guidance books.

The case has been transferred to police for further investigation, considering its seriousness, said local authorities.

According to a statement issued by the NOAPIP, 45 million illegal publications were confiscated and more than 15,000 related cases were handled in China in 2012.