WASHINGTON—Social activism organization Green America is alleging that Samsung is employing child labor at its cell phone assembly plant in China.

BEIJING—Apple Inc. supplier Pegatron Corp. began using facial recognition technology to screen applicants for its iPhone assembly plant, illustrating how some companies are guarding against the growing problem of underage workers making their way into factories in China.

SHENZHEN, China—China Labor Watch has discovered child labor at HTNS Shenzhen Co., an assembly plant that makes Samsung cell phones. This comes just two weeks after Samsung stated that it did not find any child workers while auditing the factory in September.

HUIZHOU, China—A Chinese supplier for Korean electronics giant Samsung uses children to make its products, hits workers on the factory floor, and punishes workers who make mistakes by forcing them to stand all daylong or write “self-criticism” reports, according to a labor advocacy group.

SHANGHAI—After an online tip, an inspection of an electronics factory in Suzhou, China, found more than 10 children working there.