Twenty-five bodies have been discovered by Algeria's army in the gas facility attacked by militants in the desert, private Algerian television station Ennahar said on Sunday, adding that the operation to clear the base would last 48 hours.
The bodies are believed to belong to hostages executed by the militants, said Ennahar TV, which is known to have good sources within Algerian security.
Meanwhile, Algeria's government said on Sunday the militants killed in the assault on the desert gas plant were from six different nationalities.
The official APS news agency cited Communications Minister Mohamed Said as saying they were from Arab, African and non- African countries, without providing further details. The Interior Ministry said on Saturday 32 militants had been killed.
It cited him as saying the operation to clear the Tiguentourine plant of mines laid by the militants was ongoing.
France's foreign minister on Sunday defended Algeria's handling of a hostage crisis at a desert gas plant, saying the death toll in an assault on the hostage-takers was "very high" but authorities had faced an "intolerable situation".
Islamist militants seized the remote compound in the Sahara desert before dawn on Wednesday, taking a large number of hostages. Details are still emerging of what happened when the Algerian army launched a final assault to end the siege on Saturday.
"What everyone needs to know is that these terrorists who attacked this gas plant are killers who pillage, rape, plunder and kill. The situation was unbearable," Foreign Minister Laurent Fabius said.
"It's easy to say that this or that should have been done. The Algerian authorities took a decision and the toll is very high but I am a bit bothered ... when the impression is given that the Algerians are open to question. They had to deal with terrorists," he told Europe 1 radio in an interview.
Algeria's government said on Sunday the death toll from the gas plant attacked in the Sahara desert would rise from the initial estimate of 23.