The fierceness of the fight to retake the complex by Algerian security services over four days in mid-January is still evident. Bullet holes pockmark the low, sand-color living quarters; deep gashes in one wall are a testament to the artillery fired on both sides. Between the living quarters and the plant itself, a 10-minute drive, a jumble of shredded, carbonized vehicle remnants stick out from the sand.

Still unclear was whether some of the carnage was avoidable, as officials in foreign capitals have suggested. The Algerians remain convinced their doctrine of no negotiations and maximum force was the right course of action.

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 say was 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 shut down gas production.

Others said the militants might have inadvertently cut the power during their assault, thus preventing the plant from operating.

“The plant was shut down because the terrorists blew up the generators,” said an employee at the facility who asked not to be named to avoid repercussions with his employer. The valves needed power to function, he said, and restarting the facility was a much more involved process than taking it down. “It wasn’t going to be started for a long time,” the employee said.

Outside experts said that even with rocket-propelled grenades and high-grade explosives, a natural-gas plant would have been harder to destroy than the militants may have realized. “Natural gas does not explode unless it is in a confined area,” said E. Darron Granger, the senior vice president for engineering and construction at Cheniere Energy, a liquefied natural gas terminal company.