CAIRO -- Algeria’s military launched a bloody, brazen “final assault” Saturday on kidnappers holding scores of foreigners and Algerians at a natural gas complex in the country’s east, bringing to an end four days of mayhem that left 23 hostages and 32 kidnappers dead and renewed fears that Islamist extremism is spreading in North Africa.

During Saturday’s offensive, seven hostages and 11 militants died, according to Algerian news reports. The gas plant site at Ain Aminas remained unsecure because of booby traps, British Foreign Secretary William Hague told reporters.

How many Americans were involved and their fate remained unclear even as the worst of the crisis appeared to be over.

The Obama administration on Friday acknowledged that one American had been killed, but has provided little other information.

"Today, the thoughts and prayers of the American people are with the families of all those who were killed and injured in the terrorist attack in Algeria," President Barack Obama said in a statement. "The blame for this tragedy rests with the terrorists who carried it out, and the United States condemns their actions in the strongest possible terms.”

The statement added that the United States “will remain in close touch with the government of Algeria to gain a fuller understanding of what took place” but offered no details on the fate of other Americans believed to have been at the complex.

The Obama administration has been the least forthcoming about what it has been told about events at Ain Aminas of the several nations whose citizens have been swept up in the events.

Norwegian Prime Minister Jens Stoltenberg announced that five of his citizens are missing and “eight are now safe.” Hague said six British citizens are unaccounted for. Japanese officials said 14 of their citizens remain missing. The French have confirmed that one national died and three were missing. Romania announced that one of its citizens had died.

The United States has offered no such specifics. Unofficial reports say as many as eight Americans were at the gas plant when militants attacked the site Wednesday. U.S. Rep. Michael McCaul, R-Texas, the chair of the House Homeland Security committee, told the Houston Chronicle Friday that at least one other American was missing and that another one had escaped.

Bob Dudley, the American CEO of the British oil giant BP, told reporters in a conference call that 14 BP employees were safe and four were missing. BP operates the Ain Aminas complex in partnership with Norway’s Statoil and Algeria’s state oil company.

In all, 685 Algerians and 107 foreign workers survived the ordeal, the Algerian Interior Ministry said in a communiqué.

British Defense Secretary Philip Hammond said the Algerians told his government Saturday afternoon that the crisis “had been brought to an end.”

"The loss of life as a result of these attacks is appalling and unacceptable. We must be clear that it is the terrorists who bear sole responsibility for it,” Hammond said.

In announcing the end of the hostage crisis, the Algerian Interior Ministry on Saturday provided the most detailed account to date of what had taken place.

The government said that the 32 attackers arrived in off road vehicles from “neighboring countries” Wednesday morning and began their assault by targeting a bus that was taking 19 workers to the airport. A Briton and an Algerian were killed in that episode.