The nation's trade watchdog has launched field inspections of Samsung Group affiliates on charges of operating ghost affiliate firms and conducting unfair insider trading.

The Fair Trade Commission(FTC) on Tuesday dispatched some 30 investigators to Samsung Electronics' mutual cooperation center as well as Samsung C&T, Samoo Architects & Engineers and Samsung Welstory.

The commission believes that Samoo Architects, which Samsung C&T took over in 2014, was a subsidiary in disguise from the time that it was founded in 1976.

The FTC suspects Samsung Group gave business to Samoo. 

Samwoo is the market leader in the domestic architectural design market. Last year, insider trading accounted for 60 percent of its operations.

The FTC is also looking into similar business practices at Samsung Welstory where insider trading accounted for 38 percent of operations last year.

The watchdog will continue the field inspections through next Monday.