The chief of staff of New Caledonia's president is the latest person placed under formal investigation as part of a probe into tax breaks for 3G telephone operators.
Philippe Mouton joins the President, Harold Martin, as well as a lawyer and accountant to be probed.
Prosecutors opened an investigation after administrators in the territory's postal and telecommunications office reported serious irregularities in accounts related to 3G mobile telephone operators.
Mr Martin was briefly held ten days ago amid an alleged conflict of interest.
He has denied any wrongdoing, saying allegations against him are slanderous denunciations and lies.