TIGUENTOURINE, Algeria - The goal of the heavily armed militants who seized a desert gas plant in Algeria is becoming increasingly clear: to turn the forest of pipes and tubes into a giant bomb, and to blow up everything and anyone around.

What none of them knew was exactly how, in the endless maze of metal, to do it, witnesses say.

The hundreds of workers at the plant when it was taken over last month found themselves caught between the ruthless militants on the inside and an Algerian army ringing the perimeter that was bent on showing no weakness. As the realization dawned on the captors that they, too, were essentially captives, they grew agitated and more aggressive, witnesses say. Moreover, the plant’s operations had shut down during their initial assault, thwarting their plans.

Bristling with weapons, they made their demands known to the remaining employees: restart the plant, get the compressors working again and turn the power back on.

“They pushed me very hard to restart the plant,” said Lotfi Benadouda, the Algerian plant executive whom the militants singled out as the man in charge. “Their objective was to move the hostages to the plant. They wanted to get to the factory with the hostages, and explode it.”

A more complete view of the hostage drama in the Sahara that began the morning of Jan. 16, and of the militants’ motives in carrying it out, has emerged as some of the captives provided detailed accounts of the four-day standoff, which left at least 37 foreign hostages and 29 kidnappers dead.

Their accounts contradicted some of the Algerian government’s public assertions about the crisis and supported others. At times, the government said the militants planned to destroy the gas complex and kill the hostages, but it provided no details or evidence to back up that assertion. At other times, government officials, defending a military raid on the facility, said the militants sought to flee and take captives into the desert, an assertion that some of the captives contradicted.

Now it seems clear that the siege was about more than disabling the plant, and that holding hostages for ransom was not part of the plan. Instead, the militants sought to orchestrate a spectacular fireball that could have killed everyone in the vicinity. While that plot could offer more justification for theAlgerian government’s takeno-prisoners response, questions remain about whether the standoff could have ended with fewer lives lost.

What appears increasingly certain is that the attackers benefited from inside help. They used a map to guide them around the facility, and at least one of them had once worked at the plant as a driver, officials said. But what the militants lacked was the technical expertise to execute the dramatic ending that some captives said they envisioned.

The Algerian authorities credit one of the facility’s security agents at an outer guard post with sounding a crucial alarm before being shot in the head. The guard, Lahmar Amine, has since been hailed as a national hero in the Algerian news media, and Prime Minister Abdelmalek Sellal credited him with allowing workers at the plant to shutdown gas production.

The hostage drama began before dawn on Wednesday, Jan. 16. A busload of expatriate workers was leaving the facility in an armed convoy when the attackers opened fire. The militants split into two groups, one taking over the living quarters, and the other headed for the gas-production facility, which they mined with explosives, witnesses said.

Quickly, the militants began to separate foreign workers - American, British, Japanese and Norwegian - from the Algerians, who were told they would not be harmed.

On Thursday, Jan. 17, some of the militants, who had communicated that they were protesting the French military intervention in Mali, gathered hostages laden with explosives in five vehicles. The army started firing inside the compound, wounding the militants’ leader.

The militants assembled a convoy carrying foreign hostages. What happened next is still unclear. The hostage crisis dragged on for two more days, but the events of Jan. 17 were crucial. The core of the militant operation, including its leadership, had been devastated. .

On Saturday, Jan. 19, the militants parked a car packed with explosives under two central gas-producing towers, then placed five handcuffed hostages - three Norwegians and two Americans, executives at the plant - above the car, workers said. All of the foreigners died in the resulting explosion, workers said.

Information for this article was contributed by Clifford Krauss, Henrik Pryser Libell, Martin Fackler, Makiko Inoue, Stanley Reed, Lark Turner, John F. Burns and Ravi Somaiya of The New York Times.

Front Section, Pages 5 on 02/04/2013