ALGIERS: The Islamist militants who attacked a natural gas plant in the Sahara included two Canadians and a team of explosives experts who had memorized the layout of the sprawling complex and were ready to blow the place sky-high, Algeria’s prime minister said Monday.

Militants in the highly organized operation also wore military uniforms and appeared to have had help from the inside – a man from Niger who had once worked as driver at the plant, according to accounts from the prime minister and state television.

Algeria detailed a grim toll from the attack, saying 38 hostages and 29 militants had died in four days of mayhem. Three of the attackers were captured and five foreign workers remained unaccounted for, Prime Minister Abdelmalek Sellal told reporters at a news conference in Algiers, the capital.

He did not specify the nationalities of the captured militants, report their medical conditions or say where they were being held.

Monday’s account offered the first Algerian government narrative of the four-day standoff, from the attempted bus hijacking early Wednesday to the moment when the attackers prepared to set off bombs across the gas plant, which spreads out over 5 square kilometers deep in the desert, 1,300 kilometers south of Algiers.

All but one of the dead hostages – an Algerian guard – were foreigners. The dead hostages included seven Japanese workers, six Filipinos, three energy workers each from the U.S. and Britain, two from Romania and one worker from France.

The final death toll was still unclear since accounts from other governments appeared to indicate that more than five workers were still missing. It was also lower than the 81 estimated Sunday from Algerian reports.

The militants had said during the standoff that their group included Canadians, and hostages who had escaped recalled hearing at least one of the militants speaking English with a North American accent.

In addition to the Canadians, the Algerian prime minister said the militant cell included men from Egypt, Mali, Niger, Mauritania and Tunisia, as well as three Algerians.

Officials in Canada could not immediately confirm whether two of the attackers were citizens.

The Algerian prime minister indicated that this operation was not – as the Islamists had claimed – an immediate reaction to France’s recent military intervention against Islamists in neighboring Mali, since the captured militants said it took two months of planning. But he said the group did come from northern Mali, hundreds of kilometers away from the gas plant.

He added that the group included a former driver at the complex from Niger and that the attackers “knew the facility’s layout by heart.”

They wore military uniforms, state TV reported, bolstering accounts by escaped hostages that they didn’t just shoot their way in.

“Four attackers stepped out of a car that had flashing lights on top of it,” one of the former hostages, Liviu Floria, a 45-year-old mechanic from Romania, told the Associated Press.

The prime minister said “the last words of the terrorist chief” were to slaughter the hostages.

“He gave the order for all the foreigners to be killed, so there was a mass execution, many hostages were killed by a bullet to the head,” he said.

Three Americans died in the attack and seven made it out safely, a U.S. official in Washington said, speaking on condition of anonymity because he was not authorized to speak publicly. Their bodies have been recovered, the official added.

The Masked Brigade, the group that claimed to have masterminded the takeover, has warned of more such attacks against any country backing France’s military intervention in Mali.

Norway said five of its citizens from the plant were still unaccounted for, while Japan said three Japanese were still missing. Britain said three citizens and one resident were feared dead but not accounted for. Four Filipinos and two Malaysian plant workers were also missing, according to their governments.