Police from three cities in Jiangsu, Guangdong and Hunan provinces arrested 13 suspects after a joint investigation into fake invoices, Legal Daily reported on Thursday.

More than 10.2 million copies of phony invoices were seized, along with machines that made several kinds of fake invoices, in the Aug 8 action, said Yu Bin, a police officer from Nantong’s economic investigation detachment of Jiangsu province.

Police said that an invoice purchased for 3.2 yuan (50 US cents) can be sold for 50 yuan. One machine the police seized could print 3 million yuan worth of invoices an hour.

“The profit from counterfeiting invoices is even higher than from trafficking drugs,” Yu said.

People from 23 provinces and municipalities, including civil servants and even military officers, bought the counterfeit invoices to evade taxes, according to the suspects.