Speculation about the FBI's interest in Kim Dotcom was passed across government departments and wound up in a report for ministers long before he was arrested, documents show.
Information described as "vague" was passed from one government department to another before being included in a report to Justice Minister Simon Power and Land Information Minister Maurice Williamson.
The pair were given the information in a file as they considered whether to allow Dotcom to buy the $30 million mansion he was renting.
It said there was the "possibility" the FBI "may be interested in investigating Mr Dotcom because of his ownership" of file-sharing companies.
The tip turned out to be accurate with at least four branches of government aware at least six months before Dotcom was arrested in January at the request of the FBI. He faces an August extradition hearing over charges of criminal copyright violation relating to his file-sharing company Megaupload. He denies the charges.