Magneto-electric properties (electromagneto-optical effect (EMOE)) of separate magnetic domains of yttrium iron garnets (YIGs) are investigated with using an optical polarimetry method. This local effect depends on the chosen point of optical scanning and changes essentially at scanning of various points of the domain. We have revealed separate sites of YIG sample where sharp changes of the electromagneto-optical (EMO) signal concerning average value in the domain are registered. We assume that the defect area (or its vicinity) on a surface or in volume of the investigated YIG sample causes the specified changes of EMO effect value. When probing by thin laser beam various sites of the magnetic domain, it is possible to define the defects positions by EMO signal value and it can matter for applications.