A Lebanese judge has begun questioning four pro-Syrian security chiefs detained in connection with the murder of former Prime Minister Rafik Hariri.
Hariri supporters have celebrated news of the generals' arrest
The four had earlier been formally placed under investigation for their alleged role in the car bomb attack.
The head of an United Nations-led inquiry into the killing said the men were suspected of planning the murder.
But Detlev Mehlis said that they were only part of the picture, and that more investigation was needed.
Those formally under investigation are:
- Maj Gen Jamil al-Sayyad, former head of General Security
- Maj Gen Ali Hajj, former chief of police
- Brig Gen Raymond Azar, former military intelligence chief
- Mustafa Hamdan, Republican Guard commander.
Many Lebanese blame Syria and its allies for the car bomb that killed Mr Hariri in February, but Damascus denies responsibility.
Lebanon's political landscape was transformed by Mr Hariri's death and the event led to the withdrawal of Syrian forces from the country.
Mr Mehlis' mandate from the UN Security Council ends on 15 September.
The German prosecutor has indicated that this may be extended for the completion of his investigation.