The team had checked seven locations where the Syrian government said toxic agents were stored, Xinhua reported.
Another international team tied to the United Nations is expected to arrive in Damascus Tuesday to oversee the destruction of the inventory of chemicals of the regime of President Bashar Assad.
Some chemical weapons are expected to be near the front lines of Syria's 2 1/2-year-old civil war, Organization for the Prohibition of Chemical Weapons spokesman Michael Luhan said in The Hague, Netherlands.
"This isn't just extraordinary for the OPCW. This hasn't been done before -- an international mission to go into a country, which is involved in a state of conflict, and amid that conflict oversee the destruction of an entire category of weapons of mass destruction, which it possesses," he said. "This is definitely a historical first."
The U.N. team's departure came as Syria's neighbors asked for international aid to deal with 2 million people forced to flee because of the country's extended internal conflict, the BBC reported.
"This burden is far too heavy to be borne by only the neighboring countries, said Antonio Guterres, head of the U.N. relief agency UNHCR at the opening of an international donors meeting in Geneva.
Most of the refugees -- 716,000 -- are in camps in Lebanon, the agency said. Jordan is caring for 515,000 more. Turkey says it has accepted 460,000; Iraq, 169,000, and Egypt 111,000.
Some 4.5 million are said to be displaced inside Syria.
The U.N. Security Council directed OPCW Friday to help Syria destroy its chemical weapons in the next nine months.
The intergovernmental organization, which is not a U.N. agency but cooperates with it, verifies the adherence to the Chemical Weapons Convention, which prohibits the use of chemical weapons and requires their destruction.
Assad vowed to comply with the Security Council resolution calling for the country's chemical weapons program to be dismantled and its ordnance destroyed.
"Of course we have to comply. This is our history to comply with every treaty we sign," he told Italy's RAI News 24 TV channel.
The inspectors, who arrive in Damascus Tuesday, are expected first to fill gaps in Syria's initial disclosure of its inventory of poison gases, nerve agents, delivery systems and production sites, OPCW officials said.
They will also fine-tune the logistics for visiting the sites, the officials said,
After that, which OPCW hopes will take just days, other inspectors will arrive and the reinforced contingent, including medical specialists in case of accidental contamination, will break up into field teams that will fan out to the declared weapons sites and laboratories, the officials said.
OPCW officials did not say how many locations are expected to be involved -- the Syrian declaration is confidential -- but outside experts say there are as many as 70 sites.
Under the U.N. resolution, all chemical production and mixing plants, along with equipment used for filling rockets and shells with nerve agents or sulfur mustard gas, must be destroyed by Nov. 1.
But to do that in time, the Assad regime, with international oversight, will have to use some crude methods, a senior OPCW official told the British newspaper The Guardian.
"We could fill reactors with concrete, perhaps, or they could smash them up if they're particularly delicate -- if they're glass-lined reactors, for example. Or equipment can be destroyed with explosives or by having a tank drive over it," the official said.
"We'll identify, in conjunction with our Syrian colleagues, critical pieces of equipment and then invite them to destroy them," he said. "The whole process will be conducted in a collaborative manner. It's not as if we turn up and point at something and say, 'Blow that up, drive that over that equipment, fill that with concrete.'"
Damascus has so far cooperated with OPCW, the official said. The organization submitted its initial list of inspectors Friday and got approval the next day, with no objections to any team members on the basis of nationality, the official said.
The inspectors were from about a dozen countries.
Besides the dangers of war, the inspectors dealt with temperatures rising to 95 degrees, the official said.
"At that point, we start to look into what's more hazardous -- the guys going down with heat exhaustion, the guys being exposed to toxic agents or the guys being shot at."