Olivier Hurstel, a spokesman for Roche France, said on France Inter radio on Thursday that the manufacturing process of the drug Tamiflu was "complex - a synthesis of 10 stages which takes about 12 months to complete and which involves some very delicate steps that need to be carried out in special factories protected against explosions".
"To my knowledge, industrial facilities of this type are not widespread," he said.
Roche, a giant pharmaceutical group based in Switzerland, said on Tuesday that it was prepared to share its technology with other companies and governments under licences to accelerate production, in an apparent change of emphasis in response to huge demand and political pressure for availability of the drug to be increased.
Until then, Roche, which already has some licensed partners for the drug, had indicated that it wanted to keep a tight rein on the manufacturing process to ensure quality control.
Roche has also said it is increasing production of the drug, and on Wednesday it said it expected to use a significant number of partners to boost production.
Hurstel said that Roche had increased its production capacity in a considerable way, in part by using its own factories and in part by signing partnership agreements with other factories.
Hurstel said that under current arrangements, the drug was being made in 13 factories, of which seven were not in the Roche group.
"We have increased our industrial capacity eight-fold and we shall continue to increase it, and we shall even double it"
Roche France spokesman
He said: "We have increased our industrial capacity eight-fold and we shall continue to increase it, and we shall even double it."
He said that in purely legal terms, the manufacture of the generic version of Tamiflu was not possible.
"The patent for Tamiflu runs until 2016, and what one calls a 'generic' is a product which is made when the patent has expired and has become public property.
"This possibility is not yet available, under normal conditions," he said.