The Immigration Department wrongly sent two Australian citizens to immigration detention, including one who was taken to Christmas Island, Fairfax Media has confirmed.

The two Australians, one of whom was originally a New Zealander, were taken to immigration detention following their release from prison after committing serious crimes.

One was taken to Christmas Island, while the other was detained onshore, the Immigration Department said. It would not provide further information about the date, length or circumstances of their detention, or the second individual's other nationality.