The spokesman said the evidence would have to be analyzed in the laboratories before any report is made to member states. There is no specific time line for how soon the analysis will be completed, Nesirky said.
The inspectors left Syria and flew out of Lebanon early Saturday. The team carried out a fourth and final day of inspections on Friday as they sought to determine precisely what happened in the alleged chemical weapons attack.
Nesirky said the departure of the U.N. inspection team should not be seen as any kind of a green light for military action.
"I've seen all kinds of reporting suggesting that the departure of the chemical weapons team somehow opens a window for military action of some kind," Nesirky said. "Frankly, that is grotesque, and it's an affront to the more than 1,000 staff, U.N. staff, who are on the ground in Syria delivering humanitarian aid and who will continue to deliver critical aid."
He also said any attack would leave the Syrian population vulnerable to harm.
Nesirky was pressed repeatedly on whether the inspectors would try to assign blame for the attack, and responded that the team's mandate is limited to determining whether chemical weapons were used, as agreed between Damascus and the United Nations.
In recent days, another U.N. spokesman, Farhan Haq, has said the team would build an 'evidence-based narrative" of the alleged attack that seemed to hint that they might look at how the event began.
The United States, however, has said it has gathered intelligence showing that the apparent gas attack was ordered by Assad's government, not the rebels, making the outcome of the U.N. inquiry moot if the United States launches an attack to punish Syria in the coming days.