CNN reported that Fernando Espinoza, a 29-year-old American teacher and former US Navy submariner, disappeared in Libya on November 9, five weeks after arriving in the country to start a new job at an international school in Tripoli.
His mother said he had ventured south of the city for a weekend trip to a desert oasis, but on his return was picked up for questioning, adding that the frequent texts he sent to her ceased.
The mother said she was relieved that she heard from him in a breif Tuesday's call, negotiated by the US embassy in Tunisia and Libyan authorities.
The US embassy told CNN after the call that inquiries were being handled by the State Department.
When asked by CNN for comment on Fernando's status, the State Department said they were "aware of the detention of a US citizen in Libya, saying they are monitoring the situation and due to privacy considerations, they are not going to go into specifics at this time.