The hostage crisis in eastern Algeria is over, but the questions remain.

Among them, exactly how many people are unaccounted for at a remote natural gas facility after three days of chaos that ended Saturday, leaving at least 23 hostages and dozens of Islamist militants dead.

Some 685 Algerian workers and 107 foreigners were freed, the Algerian Interior Ministry said.

Britain's BP said Sunday four of its workers remain unaccounted for. And Norway's Statoil said five of its employees were missing, while 12 others are now home in Norway, Algeria and Canada.

"Search efforts are ongoing at the gas installation, looking for more possible victims. I fear the numbers will be updated with more victims later today when the search operation is expected to end," said Mohammed Said, Algeria's communication minister.

The attackers came from six countries -- only three were Algerian -- and included Arabs and Africans, Said told state-run Radio Algeria. Algeria's military found numerous "foreign military uniforms" in its sweep of the In Amenas facility, its Interior Ministry said.

Mauritania's Sahara Media news agency said Sunday it had a video from Moktar Belmoktar, who leads the Al-Mulathameen Brigade associated with al Qaeda in the Islamic Maghreb that regional media have reported was behind the attack.

In it, Belmoktar said, "We at al Qaeda are claiming responsibility of this blessed guerrilla operation."

Belmoktar has communicated with this and other news sites before, said Andrew Lebovich, a Senegal-based security analyst. But the news agency did not post the video, and CNN has not independently confirmed its authenticity.

Eleven former hostages -- among them British citizens -- have gotten medical treatment and psychological counseling from the U.S. military at a U.S. naval base in Sigonella, Italy, a U.S. official said Sunday. The hostages were brought from Algeria to the base Friday, the official said, and are being flown to their home countries as their conditions warrant. The remains of one American hostage were also brought to the base, the official said.

In a statement Saturday night, the White House said it was in close contact with Algeria's government to "gain a fuller understanding of what took place."

British Foreign Secretary William Hague echoed those remarks, adding his government is "working hard to get definitive information" about each individual.

Japan has 10 citizens -- likely affiliated with JGC Corp., an engineering firm that was involved in gas production in In Amenas -- who are yet to be confirmed safe, in addition to a number of dead.

Such Islamist militant activity is not new to Africa, including recent violence in Mali and Somalia.

Algeria's status as Africa's largest natural gas producer and a major supplier of the product to Europe heightens its importance to those who want to invest there. Yet that interest is coupled with pressure to make sure foreign nationals, and their business ventures, are safe.

Youcef Yousfi, Algeria's energy and mining minister, insisted Sunday his country can keep its gas facilities secure and ruled out foreign forces coming in to help.

"We are going to strengthen security, and we rely first on our means and resources," Yousfi said, according to the official Algerian Press Service.

Raids turn deadly

Militants in pickup trucks struck the sprawling gas complex about 50 kilometers (30 miles) west of the Libyan border at dawn Wednesday, gathered the Westerners who worked there into a group and tied them up.

The In Amenas plant is run by Algeria's state oil company, in cooperation with foreign firms such as Statoil and BP, and because of that employed workers from several countries.

The kidnappers wielded AK-47 rifles and put explosive-laden vests on some hostages, according to a U.S. State Department official.

Algeria said the attack was in retaliation for allowing France to use Algerian airspace for an offensive against Islamist militants in neighboring Mali.

And Sahara News' report Sunday claimed Belmoktar said "40 immigrant Jihadists and supporters of Muslim countries" led the siege in retaliation for the Mali offensive.

But regional analysts believe it was too sophisticated to have been planned in just days.

On Thursday, Algerian special forces moved in because the government said the militants wanted to flee to Mali.