ALGIERS, Algeria – Algerian forces scoured the Sahara Desert on Tuesday, searching for five foreign energy workers who vanished during a chaotic four-day battle with hostage-taking Islamist militants.

One official says the men may have fled the sprawling complex during the fighting and gotten lost.

The four-day confrontation that began when al-Qaida-affiliated militants stormed the remote desert natural gas complex and took captives was punctuated by exploding cars, attacks from helicopters and a final assault by Algerian special forces.

In all, 37 hostages, including an Algerian security guard, and 29 militants were killed, but five other foreign workers remain missing.

“Are they dead? Did they attempt to flee the site after the attack like some other expatriates? Are they lost in the desert after taking a wrong turn?” said an official who is part of Prime Minister Abdemalek Sellal’s office.

The Ain Amenas gas plant, jointly run by BP, Norway’s Statoil and the Algerian state oil company, is deep in the Sahara, about 800 miles south of the Mediterranean coast, with few population centers nearby.

More than 700 people work at the facility, including 130 foreigners from 26 countries who were targeted by the militants. The Islamists caught many of those foreign workers and wrapped some with explosives to use as human shields.

Many foreign and Algerian workers hid and then slipped out of the sprawling facility into the hard, featureless desert, eventually reaching the Algerian soldiers who had surrounded the complex.

The $2 billion complex, which came online in 2006, was showing signs of life again Tuesday. Dozens of workers swarmed in to clean it up after experts went through and removed explosives that had been planted by militants.