The raids followed a 12-month investigation by US Immigration and Customs Enforcement (ICE) into who was importing the chips and selling them on. Typically the chips are made overseas before being shipped to dealers in the US or other nations.

'Illicit devices'

"Illicit devices like the ones targeted today are created with one purpose in mind, subverting copyright protections," said Julie L. Myers, assistant secretary of Homeland Security for ICE in a statement.

"These crimes cost legitimate businesses billions of dollars annually and facilitate multiple other layers of criminality, such as smuggling, software piracy and money laundering," said Ms Myers.

Raids were carried out across many US states including California, Florida, Hawaii and New York. No details of who was arrested have been released.

Mod chips for the Nintendo Wii seem to be growing in popularity. ICE said it had helped Nintendo seize more than 61,000 Wii mod chips since April 2007.

According to figures released by ICE, counterfeiting and piracy costs the US up to $250bn (£125bn) every year.