Clare Morgana Gillis, 34, of New Haven was taken captive Tuesday and was believed to be in government custody in Tripoli Sunday, The Atlantic said.
Also being held are American James Wright Foley, a writer for GlobalPost, and Spanish photographer Manuel Varela de Seijas Brabo. The magazine could not confirm whether South African photographer Anton Lazarus Hammerl, who was detained with the others, was being held at the same site.
Unlike journalists previously detained in Libya, they have not been seen by diplomats or reporters.
Gillis also has worked for USA Today and The New Republic, her father Robert told The Hartford Courant Monday. He said Human Rights Watch called him and his wife Jane to inform them of the detention.
Clare Gillis is a former Fulbright Scholar with a doctorate in history from Harvard.