Major computer chip equipment maker slot ASML says a former employee in China stole information about its technology.
The Dutch firm says it has since reported the breach to authorities in the Netherlands and the US.
However, the company added that it does not "believe that the misappropriation is material to our business."
ASML is one of the most important firms in the global microchip supply chain. It makes machines that produce the world's most advanced chips.
Chips, or semiconductors, which are used to power everything from mobile phones to military hardware, are at the centre of a bitter dispute between the US and China.
"We have experienced unauthorised misappropriation of data relating to proprietary technology by a (now) former employee in China," ASML said
"As a result of the security incident, certain export control regulations may have been violated. We are implementing additional remedial measures in light of this inciden