Related על דמאי 6:11

[Produce purchased in] Cheziv [=Achziv, a town in northern Israel] alone is exempt from Demai (cf. Dem. 1:3). [But] the presumption is that [produce purchased elsewhere in] the Land of Israel is liable, unless it is known [with certainty] that it is exempt. [Conversely] the presumption is that [produced purchased] outside the Land of Israel is exempt until it is known [with certainty] that it is liable. [One who purchases produce from] Israelite landowners [who are presently residing] in Syria need not separate Demai [for the purpose of tithing], but if it is known that the majority of the produce is theirs (i.e., grown on their land in Israel), behold, it is liable.