Reporting on militants' seizure of workers at a natural-gas complex in eastern Algeria has been a special challenge, in part because outside journalists need a visa and accreditation before they can enter the country.

Access to live information from the Sahara Desert facility -- which British Prime Minister David Cameron this week noted was "one of the most remote places in the world" and about "18 hours by road from the capital, Algiers" -- is hard to come by, and conflicting accounts have emerged about the hostages and other aspects of the story.

Here is a look at what CNN has reported from official sources; what CNN has reported from other news media; and some unanswered questions:

WHAT OFFICIAL SOURCES SAY

Initial attack on Wednesday

-- The incident began when militants attacked workers who were traveling from In Amenas gas field to the In Amenas Airport early Wednesday, Algerian Interior Minister Diho Weld Qabilyeh told Algerian state television. Two people, an Algerian and a Briton, were killed in that attack, according to Algerian and British officials.

-- After security forces accompanying the workers returned fire, the militants went to the gas installation itself and took hostages, Qabilyeh told Algerian state television.

-- The remote gas field, about 37 miles west of the Libyan border and about 800 miles from the Algerian capital, Algiers, is run by "a joint venture of the Algerian national oil company Sonatrach, (Britain's) BP and (Norway's) Statoil," according to BP.

Initial hostage situation

-- The militants, equipped with AK-47 rifles, reportedly put explosives-laden vests on some of the hostages, a U.S. State Department official said.

-- While Algerian media reports indicated that militants initially had hundreds of hostages, including dozens of foreign workers, CNN doesn't have from official sources clear information on the number and the nationalities of the people who have been held.

-- Officials from the United States, the United Kingdom, Norway, France, Malaysia, Japan and Ireland have said their nationals were among those involved.

Algerian military attacks; more casualties; some hostages escape

-- On Thursday, Algerian forces attacked the militants as they were preparing to move the hostages in vehicles, Algerian Communications Minister Mohamed Said told state television.

-- Thursday's military operation left an unspecified number of people dead and injured, Said told state television.

-- One French citizen was killed and three others were saved in the operation to free hostages, the press office of the Ministry of Foreign Affairs in Paris said Friday.

-- However, since Wednesday, some people have been freed or have escaped. Ireland's government confirmed that one of its citizens, Stephen McFaul, escaped Thursday.

-- McFaul made a break for freedom after a vehicle he was in -- one of several targeted by Algerian fighters -- crashed, with his captors' explosives still around his neck, his brother Brian McFaul told CNN from Belfast.

-- Before Thursday's military raid, some hostages had disguised themselves to escape, according to Regis Amoux, chief executive of the CIS catering firm that had 150 workers who were freed.

-- The United States on Friday was evacuating between 10 and 20 people, a U.S. defense official told CNN. They will be taken to U.S. facilities in Europe, the official said, and the condition of those who are injured will be assessed.

-- BP said Friday that a "small number of BP employees" are still unaccounted for, while Statoil said the fate of eight of its employees at In Amenas was still uncertain. Nine other Statoil workers who were at the plant are safe, it said.

-- By Thursday night, some Americans had been freed and had spoken with relatives back home, while others remained unaccounted for, U.S. officials said.

-- A State Department official told CNN Wednesday that the abductors are demanding that members of their group who are being held prisoner elsewhere be released and sent to northern Mali. U.S. State Department spokeswoman Victoria Nuland said Friday that the United States will not negotiate a prisoner exchange with the militants. CNN has not confirmed whether any Americans still were being held.

WHAT CNN HAS REPORTED, CITING OTHER NEWS MEDIA

Number of dead