The military also is investigating if an insider helped the militants whose attack led to the four-day hostage crisis at the Ain Amenas complex, the officials said. That probe comes amid unconfirmed reports that BP energy executives were holding a meeting at the site when the attackers arrived, and that the militants sought them out.
The al-Qaida-affiliated militants stormed the desert gas complex near the Libyan border on Jan. 16, taking hundreds of people—most of them Algerians—hostage. The resulting fight with the Algerian army ended with at least 37 hostages and 29 militants killed. At least 36 of the dead hostages were foreigners.
The Algerian army has largely neutralized al-Qaida's branch in the populated north of the country. But the Ain Amenas attack was carried out by a group based far to the south in northern Mali, where Islamist extremists have flourished but are now under attack from French-led forces.
Army Chief of State El-Gadid Salah consulted regional military chiefs and the decision was made to deploy the army around oil and gas sites in the south as well as electrical plants in the north, officials told journalists on condition of anonymity because they were not authorized to speak to the press.
Whether the militants had inside help remains unclear.
Algeria's prime minister has said that a former driver who worked at the gas complex was involved with the attackers. Separately, executives with the state oil company Sonatrach, which manages the site along with BP and Norway's Statoil, said that a meeting of BP executives was going on the day the plant was assaulted.
"We are convinced that there was complicity on the inside because when the terrorists arrived at the site, they asked for the VIPs," deputy plant director Salim Hadjersi told reporters visiting the site Thursday. "How could the terrorists know there was going to be an important meeting of BP executives, including some coming from London?"
BP spokesman Toby Odone would not discuss the possibility of an insider attack or confirm that high-level executives were meeting at Ain Amenas on Jan 16.
"We don't talk about our executives' meetings normally," he said. "We're not going to speculate or feed that speculation."
At least one BP executive was killed in the attack. Carlos Estrada, originally from Colombia but a London resident, was vice president of the company's upstream global projects and was visiting the site.
The Algerian government also has formed an inter-departmental commission headed by Prime Minister Abdelmalek Sellal to examine the attack. It includes members from the ministries of defense, interior, foreign affairs, labor and energy, said an official, who also requested anonymity because he was not authorized to talk to the press.
The Ministry of Energy, meanwhile, is working with British and U.S. experts to review the damage to the gas complex and determine when or if production can restart.
Lotfi Benadouda, the head of the plant, told journalists visiting Thursday that he expected at least one of the three gas units would go back into production "soon," but he did not give a more exact timeframe.
Associated Press reporter Cassandra Vinograd contributed to this report from London.