Gruenhelme e.V. Says Bernd Blechschmidt, Ziad Nouri and Simon S, whose last name wasn't provided, were taken by unknown persons from the town of Harem in Idlib district on May 14.
The group's founder, Rupert Neudeck, told The Associated Press today that a fourth staff member managed to avoid capture and is safe.
Neudeck says the aid group kept the kidnapping secret so as not to jeopardise their safety but all efforts to determine who they are being held by were unsuccessful.
