Dutch semiconductor equipment maker ASML said on Thursday that a U.S. software subsidiary was the victim of corporate theft several years ago, but the information stolen was not rekate dto its high-end lithography machines.

Dutch business daily newspaper Financieele Dagblad first reported that technology had been stolen by high-level Chinese employees at ASML’s research and development department and leaked to a company linked to the Chinese government.

ASML said “we discovered this theft ourselves” and took immediate action. It said the technology stolen was not core to its business, and added it was still able to operate in China.

“This affected a small part of our company in Silicon Valley where software programs for machine optimalization are developed,” ASML said in a response.

“It’s not as if a blueprint that you could use to build a lithography system is lying on the street.”

ASML said information about the incident is available in public U.S. court documents.

ASML is the sole maker of EUV lithography systems, used to manufacture advanced semiconductor chips.

The court awarded ASML $223 million in damages.

In 2015, ASML disclosed a breach of its computer systems, but said at the time damage from the hack was limited and released few further details.