Song met the former detainees in Zintan following their release, the ICC said in a release.
"The ICC is grateful to the Libyan authorities for their agreement today to release the Court's staff members so that they can be reunited with their families," Song said during a press conference in Zintan Monday.
The four ICC staff members -- Alexander Khodakov, Esteban Peralta Losilla, Melinda Taylor and Helene Assaf -- were detained in Zintan following their visit to Saif Al-Islam Gadhafi, son of late Libyan leader Moammar Gadhafi, on June 7 to ensure the rights of the defense in his upcoming ICC case were being preserved.
Gadhafi is on trial for charges of crimes against humanity for his alleged role in the killing of protesters during the uprising last year that led up to the overthrow of his late father, Moammar Gadhafi. He has denied the charges against him.