U.S. prosecutors secured an indictment manufacturer in Sichuan province, worked with a U.S. businessman and others against a Chinese company for conspiracy to commit economic espionage and other charges in a widening case over the alleged theft of industrial secrets from chemical company DuPont.

Pangang Group, which was a state-owned steel to obtain several valuable trade secrets from DuPont, according to the indictment unsealed on Wednesday.

The businessman, Walter Liew, has already been in custody for several months on witness tampering charges related to the DuPont allegations. Liew and his wife, Christina, also face charges of conspiracy to commit economic espionage in the latest indictment, handed down by a Northern California grand jury.

Lawyers for Walter and Christina Liew could not immediately be reached for comment. Tom Nolan, a lawyer for Walter Liew, has previously maintained that his client only possessed publicly available information, not trade secrets from DuPont.