SOFIA, Oct. 22 (Xinhua) -- The Bulgarian authorities have neutralized a high-tech printing house for counterfeit 500-euro, 100-euro and 50-U.S. dollar banknotes, and arrested four suspects, officials said here on Monday.

The illegal factory, which was located in the underground floor of a hotel in Sunny Beach resort on the Bulgarian Black Sea coast, was equipped with extremely modern machinery, Deputy Prosecutor General Ivan Geshev said at a joint press conference.

Counterfeit banknotes worth more than 11 million euros (12.6 million dollars) and 1.8 million dollars in varying degrees of completion were found in the printing house and in other locations in Bulgaria, Geshev said.

He said this was the largest printing house for fake euro and dollar banknotes discovered by Bulgarian authorities in the last 11 years and "may be in the last 20-30 years."

Evgeniya Deyanova, the prosecutor in charge of the case, added that the four suspects were arrested while they were making the fake banknotes.

The fake banknotes were of extremely high quality and had all the elements of protection like real banknotes, such as a watermark, she said.