1:55: CNN reports that explosives-laden vests were put on some of the hostages, according to U.S. officials.
The White House did not specify the number of current hostages that are Americans, though a total of five foreign hostages have reportedly been freed.
CNN also confirms that a U.S. drone has been sent to the plant to monitor the situation and send back intelligence.
1:37 p.m.: ANI, the Mauritanian news agency that has been in contact with the militants, there are seven hostages remaining, two of whom are American. There are no confirmed American casualties.
1:35 p.m.: Also via Al-Jazeera, French President Francois Hollande said the hostage crisis vindicates France's recent military operation in Mali.
The Qatar-based news agency added that Japan's Vice Foreign Minister Minoru Kiuchi, who "is now in Algeria, urged the Algerian government to put an "immediate end" to the military operation."
