Militant group Ansaru says 7 foreign workers are dead . Ansaru is believed to be an offshoot of Boko Haram , U.S. officials say . ( CNN ) -- Comment: The foreigners worked for a construction firm in northern Nigeria .
Militant group Ansaru says 7 foreign workers are dead . Ansaru is believed to be an offshoot of Boko Haram , U.S. officials say . Comment: The foreigners worked for a construction firm in northern Nigeria .