The captains of the vessels were jailed last week for illegally fishing in New Caledonia's waters but their crews fled from Noumea despite the authorities disabling their navigation gear.
According to the public broadcaster, a naval commander of the French navy has been told by Australia that the two vessels have not entered its zone.
The commander said the vessels may have headed north towards Papua New Guinea or Vietnam.
He said the surveillance of the territory's maritime zone was challenging because the military has just two aircraft to oversee one million square kilometres of ocean.
The so-called "blue boats" have been caught in several countries and territories over the past few years including Palau, the Federated States of Micronesia, Papua New Guinea, Indonesia, Australia and, recently, in New Caledonia
Photo: AFP Vietnamese fishing boats.