The number of bodies found in an Algerian gas plant continues to rise a day after special forces stormed the complex, bringing a four-day siege to an end.

Algerian officials said Sunday that 25 more bodies were located inside the Ain Amenas natural gas complex, where radical Islamists held dozens of foreign workers captive during a bloody standoff. The official, who spoke on the condition of anonymity, told The Associated Press that the bodies were badly disfigured and it was difficult to determine their identity.

"The bodies could be either Algerian or foreign hostages," he said.

On Saturday, Algerian special forces launched a final assault on the gas plant. At the time, authorities estimated that 23 hostages and 32 militants died during the ordeal, but the numbers were expected to rise.

A government spokesperson said Sunday the militants came from six countries and were armed to cause the maximum amount of damage to the facility, located in the Sahara desert.

Officials said the complex was rigged with multiple explosives.

“They had decided to succeed in the operation as planned, to blow up the gas complex and kill all the hostages," said Communications Minister Mohamed Said, speaking during an interview on state radio.

British Prime Minister David Cameron confirmed that three Britons were killed in the siege and another three were feared dead. He said 22 citizens who survived the attack had returned to Britain.

Foreign Affairs Minister John Baird said Sunday that no Canadians are believed to have been among the hostages and one citizen who was reported to be on the gas plant site has safely left Algeria.

According to ABC World News on Sunday, one of the survivors said a captor “spoke excellent English and may have been from Canada.” Ottawa has said it's "pursuing all appropriate channels to seek further information" and is in close contact with Algerian authorities.

The militants included individuals from various countries, including Mali, Egypt, Niger and Mauritania.

Radical Islamists linked to al Qaeda stormed Ain Amenas, which employed hundreds of foreign workers, on Wednesday and held them hostage for four days as the Algerian military surrounded the complex.

Through the crisis, the Algerian government maintained that it would not negotiate with the terrorists, choosing military actions instead.

A total of 685 Algerian and 107 foreigner workers were freed over the course of the standoff, the Interior Ministry statement said, adding that the group of militants that attacked the remote complex consisted of 32 men of various nationalities, including three Algerians and explosives experts.

The militants came from a Mali-based al Qaeda group run by an Algerian. The rebels initially said the attack was in response to France’s intervention in Mali, where Islamists militants have taken control of the large portion of the country’s north.

An audio recording of discussions between Algerian security forces and the head of the kidnappers, Abdel Rahman al-Nigiri, shed light on hostage-takers’ demands, which appeared to focus on a prisoner-swap.

“You see our demands are so easy, so easy if you want to negotiate with us," al-Nigiri said in the recording broadcast by Algerian television. "We want the prisoners you have, the comrades who were arrested and imprisoned 15 years ago. We want 100 of them."

In a separate recording, al-Nigiri described how the Algerian army on Thursday had killed half the militants and that he was prepared to blow up the remaining hostages if forces attacked again.

Retired Lieutenant-General Andrew Leslie, who was the deputy commander of International Security Assistance Force in Afghanistan, said the poverty in Mali helps breed terrorism.

“It’s a desperately poor region,” Leslie told CTV’s Question Period on Sunday. “Swarms of mainly angry young men who don't have great job prospects or indeed a long life expectancy, and they're looking in many cases for a cause, and challenges to authority, challenges to the status quo. So as the movement spreads, as it gains momentum, that will attract more converts.”

With files from The Associated Press