CHICAGO (BLOOMBERG) - A software engineer for a locomotive manufacturer in a Chicago suburb was charged with stealing trade secrets and sharing them with a company in China where he now works, according to US prosecutors.

Xudong "William" Yao, 57, was accused in an indictment of nine counts of trade secrets theft and is believed to be living in China, prosecutors said in a statement on Thursday (July 11).

Yao, who was born in China but was a naturalised US citizen, allegedly stole copies of more than 3,000 electronic files that contained proprietary technical information and software source code, according to the statement. The Chicago-area company wasn't identified.

The theft began just two weeks after Yao began working for the US company in 2014 and lasted for about six months until February 2015, according to the indictment. During that period, Yao allegedly sought and later secured a job with a Chinese company that provides automotive GPS-locating systems. The Chinese company also wasn't identified.

Yao was fired from the Chicago-area company for unrelated reasons a few months before he left for China. He allegedly took nine copies of the stolen source code and information about how the code worked, according to the indictment.

Yao was charged in December 2017, but the indictment remained sealed until Wednesday, according to prosecutors.