Hamas authorities in the Gaza Strip broke up a counterfeiting ring that had printed millions of shekels worth of fake money, the organization said Sunday.

Police spokesman Ayyoub Abu Shaar said that authorities uncovered the ring last week when they traced a man trying to use a counterfeit 100-shekel bill last week. The Palestinian territories use Israeli currency for many transactions.

The man led authorities to a gang and some NIS 20 million, or roughly $5.5 million, in fake bills. Abu Shaar says the money was confiscated before it was put into circulation.

Abu Shaar says police have arrested four people so far, and confiscated equipment including printers, laptops, ink and paper.

It is the largest counterfeiting ring discovered in Gaza since Hamas took control in 2007.