The Turkish authorities are carrying out blood tests on Syrians who have fled the fighting at home to determine if they have been victims of chemical weapons, a medical source said Monday.
"Samples have been taken from people wounded in Syria who have been transported to Turkey," the source said on condition of anonymity, adding that the results were not yet known.
Western nations have raised concerns about the use of chemical weapons in the escalating conflict between the regime of President Bashar al-Assad and rebels fighting to oust him.
Top UN rights investigator Carla del Ponte said Sunday that according to testimony, rebels have been using sarin gas.
US President Barack Obama has refused to rule out any options, but has said he did not foresee deploying US troops if Assad's regime is proved to have used chemical weapons.
Turkish Prime Minister Recep Tayyip Erdogan, a one-time Syria ally, on Sunday branded Assad a "butcher" and a "murderer" who would pay a heavy price for the killings in Syria.