Andrada's vehicle overturned allowing him and a few others to escape. He sustained cuts and bruises and was grazed by a bullet on his right elbow. He later saw the blasted remains of other vehicles, and the severed leg of one of the gunmen.
The site of the gas plant spreads out over several hectares (acres) and includes a housing complex and the processing site, about a mile apart, making it especially complicated for the Algerians to secure the site and likely contributed to the lengthy standoff.
"It's a big and complex site. It's a huge place with a lot of people there and a lot of hiding places for hostages and terrorists," said Col. Richard Kemp, a retired commander of British forces who had dealt with hostage rescues in Iraq and Afghanistan. "These are experienced terrorists holding the hostages."
Casualty figures varied widely. While the Algerian government has only admitted to 19 hostages dead so far, the militants claimed through the Mauritanian news website ANI that the helicopter attack alone killed 35 hostages.
One American, from Texas, is among the dead and least one Briton, a Frenchman and Algerians have also died in the standoff. Escaped Algerian workers describe seeing people of many nationalities, including Japanese, shot down.
French Defense Minister Jean-Yves Le Drian said Saturday that the Frenchman killed, Yann Desjeux, was a former member of the French special forces and part of the security team. The remaining three French nationals who were at the plant are now free, the Foreign Ministry said.
British Foreign Secretary William Hague confirmed that as of Saturday, there were "fewer than 10" British nationals still at risk or unaccounted for and "the majority of" Britons at the plant were now safe, he said.
Statoil CEO Helge Lund said Saturday that there were only six Norwegians unaccounted for, from the 17 at the plant at the time of the attack. BP said four of its 18 employees were still unaccounted for.
Romanian Prime Minister Victor Ponta said Saturday one Romanian hostage was killed in the course of the siege, while four escaped unharmed.
The attack by the Mali-based Masked Brigade, founded by Algerian militant Moktar Belmoktar, had been in the works for two months, a member of the brigade told the ANI news outlet. He said militants targeted Algeria because they expected the country to support the international effort to root out extremists in neighboring Mali and it was carried out by a special commando unit, "Those Who Signed in Blood," tasked with attacking nations supporting intervention in Mali.
The kidnappers focused on the foreign workers, largely leaving alone the hundreds of Algerian workers who were briefly held hostage before being released or escaping.
Several of them arrived haggard-looking on a late-night flight into Algiers on Friday and described how the militants stormed the living quarters and immediately separated out the foreigners.
Mohamed, a 37-year-old nurse who like the others wouldn't allow his last names to be used for fear of trouble for himself or his family, said at least five people were shot to death, their bodies still in front of the infirmary when he left Thursday night.
Chabane, who worked in food services, said he bolted out the window and was hiding when he heard the militants speaking among themselves with Libyan, Egyptian and Tunisian accents. At one point, he said, they caught a Briton.
"They threatened him until he called out in English to his friends, telling them, 'Come out, come out. They're not going to kill you. They're looking for the Americans,'" Chabane said.
"A few minutes later, they blew him away."
Paul Schemm reported from Rabat, Morocco. Associated Press writers Aomar Ouali and Karim Kebir in Algiers; Oliver Teves in Manila, Philippines; Elaine Ganley in Paris; Sylvia Hui in London, and Jan M. Olsen in Copenhagen contributed to this report.