A former Apple employee pleaded not guilty on Monday after federal prosecutors filed an indictment accusing him of stealing trade secrets.

Federal officials on July 12 indicted Xiaolang Zhang on a single count of trade secret theft, alleging that Zhang had stolen a 25-page blueprint for a circuit board designed to be used in an autonomous vehicle, according to the indictment filed in US District Court for the Northern District of California.

The formal indictment followed a filing by a Federal Bureau of Investigation agent on July 10 describing the charge and Zhang’s arrest at a Silicon Valley airport before boarding a flight to China.

Zhang pleaded not guilty at a hearing on Monday in San Jose. He had been provisionally appointed a public defender, but has retained his own lawyer, Daniel Olmos.

Olmos declined to comment on the case. A spokesman for the US Attorney for the Northern District of California declined to comment beyond the indictment.