But, Syria first will have to approve their composition and mandate.

The Netherlands-based Organization for the Prohibition of Chemical Weapons is expected to appoint a team of eight to 10 experts in chemistry and medicine.

Amy Smithson, a senior fellow of the Monterey Institute of International Studies, says the investigators have strict guidelines for how to collect suspected chemical samples and deliver them to specialist labs.

"What is going to be important for international credibility is that any samples be taken with a chain of custody that proves this is where this sample was taken, and that it stayed in a legal chain of custody to the point of analysis so that those results will stand up in front of an international legal court or the international court of opinion," she said.

Smithson says the investigators may find that commercial chemicals were used in Khan al-Asal -- rather than highly-lethal warfare agents like mustard or nerve gas, as seen here in a Russian stockpile that was destroyed voluntarily in 2002.

"The chemical weapons convention defines chemical weapons as those classic warfare agents and their delivery systems and any toxic chemical used for military purposes," Smithson explained. "So it does not matter if it is ethyl methyl [an industrial solvent] or VX, which is a nerve agent. You cannot cross that line."

Syria's rebel factions have denied using any chemical weapons in their battle to oust autocratic President Bashar al-Assad.