China Labor Watch said it had found more than 10 children working at the factory of a China-based supplier for the technology giants Samsung Electronics and the Lenovo Group in an investigation in July and August.

The group, based in New York, also said its investigation had found more than 100 student workers who were not being paid overtime wages or a subsidy for working at night.

The supplier, HEG Technology, denied the accusations, and Samsung said it had found no children or students working on the Samsung production line at the factory, in Huizhou. A Lenovo spokeswoman said the company would look into the report.

In a statement, China Labor Watch said it shared evidence with Samsung last week and that Samsung had demanded that the supplier pay some students’ wages. But it did not say whether Samsung had acted on the matter of child labor or whether it had provided the information to Lenovo.