(USA TODAY) -- A U.S. official says two more Americans were killed in the hostage standoff at a natural gas complex in Algeria, making the final U.S. death toll to three U.S. citizens, according to the Associated Press.
Seven Americans made it out safely.
The official said Monday that the FBI had recovered the bodies of the Americans and notified their families. The official had no details on how the Americans died. He spoke on condition of anonymity because he wasn't authorized to speak publicly on the matter.
At least 37 hostages from eight countries were killed during a four-day siege at an the complex, Algerian Prime Minister Abdelmalek Sellal said Monday.
Five foreign workers remain unaccounted for, Sellal said. He said 32 terrorists were killed during assaults by Algerian military forces to end the standoff and "a few" may have escaped.
Sellal said the terrorists came from Egypt, Canada, Mali, Niger, Mauritania and Tunisia, and that three were captured.
Algerian special forces stormed the plant on Saturday to end the siege, moving in to thwart what government officials said was a plot by the Islamist terrorists to blow up the complex and kill all their hostages with mines sown throughout the site.
On Sunday, Algerian bomb squads sent in to blow up or defuse the explosives found 25 bodies, said a security official, who spoke on condition of anonymity because of the sensitivity of the situation.
"These bodies are difficult to identify. They could be the bodies of foreign hostages or Algerians or terrorists," the official said.
In addition, a wounded Romanian who had been evacuated died, raising the overall death toll to at least 81.
Algerian spokesman Mohamed Said said Sunday that he expects the death toll to rise.
"I am very concerned that this preliminary death toll will be, unfortunately, revised upwards in the coming hours," he said.
Special forces continue to secure the facility and look for more victims, Said added.
On Monday, Philippine Foreign Affairs officials said six Filipinos were among the hostages killed. Spokesman Raul Hernandez told reporters that 16 Filipinos have been accounted for and four others are still missing.
British Prime Minister David Cameron said Sunday three Britons were killed and another three are believed dead, as is a British resident.
"Now, of course, people will ask questions about the Algerian response to these events, but I would just say that the responsibility for these deaths lies squarely with the terrorists who launched a vicious and cowardly attack," Cameron said.
Norwegian Prime Minister Jens Stoltenberg said his country is awaiting word on five missing workers.
"We have to face the fact that Norwegian lives might have been lost," he said. "But we also have to feel relief that (eight) have been already saved."
One American, Frederick Buttaccio of Texas, was confirmed dead Friday. The Algerian government reported that 685 Algerian and 107 foreigner workers were freed during the four-day standoff.
In the final assault Saturday, the remaining band of militants killed seven hostages before 11 of them were in turn cut down by the special forces, Algeria's state news agency said. The military also said it confiscated heavy machine guns, rocket launchers, missiles and grenades attached to suicide belts.
The Algerian government defended its actions against the al-Qaeda-linked group who call themselves "Signers in Blood."
"The terrorists were determined to be successful in their operation; they had planned to blow up the gas complex and execute all the hostages," Said said, citing the "sophisticated arsenal" of weapons recovered.
The State Department issued a travel warning Saturday night for Americans in or traveling to Algeria, citing credible threats of the kidnapping of Western nationals. The department also authorized the departure from Algeria of staff members' families if they choose to leave.
Militants attacked the Ain Amenas gas plant early Wednesday after initially assaulting a bus with facility workers en route to the local airport.
The terrorists, made up of at least six nationalities, then retreated to two different sections in the facility. Algerian special forces began an assault on the facility to free the hostages Thursday, in a move that took Western nations by surprise because they weren't consulted beforehand.
Algeria has been fighting a war against militants for two decades and refuses to negotiate with terrorists.
After Saturday's assault, French President Francois Hollande gave his backing to Algeria's tough tactics, saying they were "the most adapted response to the crisis."
"There could be no negotiations" with terrorists, the French media quoted him as saying in the central French city of Tulle.