New Zealand police have been praised by the White House for their role in the case against Kim Dotcom.

But the extent of that praise is a secret in New Zealand - police headquarters says any thanks from the United States would be covered by a confidentiality clause applied to correspondence with foreign law enforcement agencies.

Dotcom and three others were arrested by the New Zealand police's elite special tactics group in January as part of an FBI operation against his Megaupload website, which is accused of being a front for huge internet piracy.

The US attorney prosecuting the case, Jay Prabhu, was present at the North Shore Police Station in Albany - just kilometres from Dotcom's mansion - during the raid.


The operation was timed by the FBI to unfold across the world at the same time as Hong Kong's Customs and Excise staff were carrying out raids on the company headquarters.

Images published by the US Consulate General in Hong Kong show its diplomatic staff presenting a plaque of appreciation to local law enforcement officers involved in the raid.

In a letter, FBI director Robert Mueller told Hong Kong's Customs and Excise Department that its help on the Megaupload operation "was essential to conducting successful enforcement actions".

Officials at police headquarters in Wellington have refused to say whether a similar expression of thanks had been made to New Zealand officers. A spokesman said it would be classified as "correspondence between New Zealand Police and overseas law enforcement agencies".

The efforts of those involved in the raid have already earned the thanks of President Barack Obama's head copyright enforcer.

Victoria Espinel, the US Intellectual Property Enforcement Co-ordinator for the White House, singled out the help from officers in "New Zealand, Hong Kong, the Netherlands and Germany" in the Megaupload case as being "the exception". She told the US Senate Committee on the Judiciary "the investigation could not have moved forward without the assistance of foreign law enforcement that was willing to co-operate".