As the hostage situation at an Algerian oil field has been declared officially over, a host of questions remain. Initial reports said 16 foreign hostages were freed on Saturday, but nationals from Norway, Japan, Britain and the U.S. remain unaccounted for. The hostage takers said they attacked the facility in retaliation for a French offensive against Islamist rebels in neighbouring Mali. The incident raises larger questions about the threat of militant takeovers elsewhere in the Sahara-- filled with foreign firms in mining, petroleum, transport and construction. In the town of In Amenas, where the gas plant is located, residents are concerned for their safety, and for the future. (SOUNDBITE) (Arabic) IN AMENAS RESIDENT SAYING : "Now I think all the French companies want to leave and won't provide jobs, this is the problem. We were working and all was fine but now after this it is over, everything will stop, there will be a big labour crisis." Experts say porous borders and ill-equipped security further increases the threat of militant attacks. And with little improvement in the daily lives of people living in some of the world's poorest countries, recruitment of members into Islamic organisations has become easier.