France sent a helicopter carrier and forensic police to Beirut after the city's port was almost completely destroyed by a massive explosion.
Both Lebanese protesters and the international community have called for an impartial investigation into the incident that killed more than 170 people and injured thousands.
The Lebanese judicial investigation began with political wrangling over the naming of a lead investigator. Many are doubtful the government can carry out an impartial investigation.
A US envoy also arrived at the port on Saturday to help investigate the explosion.
"What exactly happened? What led to the circumstances for this explosion? We really need to make sure that there is a thorough and a transparent, credible investigation, I know that's what everyone is demanding," diplomat David Hale said.
Meanwhile at a commercial part of the port that was not damaged by the blast, workers were unloading wheat. The United Nations says 30 percent of the port remains operational.
On Friday families of the dead, as well as some of the survivors, called on the UN Security Council for an international investigation.
President Michel Aoun has rejected the idea.
However French teams have already been at work, sending divers into the underwater crater created by the explosion and taking samples of explosives.
The cause of the August 4 fire that ignited nearly 3,000 tons of ammonium nitrate at Beirut’s port remains unclear.
Documents have emerged showing the country’s top leadership and security officials were aware of the chemicals stored at the port.