A tip from US Customs has led Guam airport agency and local customs officials finding surveillance cameras and listening devices hidden in security-sensitive areas.
The two agencies' top officials said they were unaware the devices had been installed, including in areas where arriving passengers and their bags and other belongings are checked.
The Customs and Quarantine Agency Director Rick Blas says the FBI has been notified.
Mr Blas says he does not know if anything has been compromised but it is possible the confidentiality of individuals being inspected and interviewed by customs officers may have been breached.
He says if information was breached, the civil rights of passengers might become an issue.
Mr Blas says there also may have been monitoring narcotics arrests.
The Pacific Daily News reports some of the finger-nail sized cameras were concealed in square "EXIT" sign boxes.
Airport officials say they cannot remember any authorisation for the installation of the cameras and there has never been authorisation for listening devices at the airport.