TULSA, Okla. (AP) — Federal prosecutors said Friday that a Chinese national employed by an Oklahoma petroleum company has been charged with stealing trade secrets.

Authorities said Hongjin Tan, 35, is accused of stealing trade secrets from his unnamed U.S.-based employer that operates a research facility in the Tulsa area.

An affidavit filed by the FBI alleges that Tan stole trade secrets about an unidentified product worth between $1.4 and $1.8 billion to his employer to benefit a Chinese company where Tan had been offered work.

Authorities say Tan allegedly downloaded hundreds of computer files, including research reports, regarding the manufacture of a “research and development downstream energy market product.”

The reports described not only how to make the product, which the company says “is a complicated and technically difficult process,” but also the company’s plans to market the product in China and in cellphone and lithium-based battery systems, according to the affidavit.

“These files included information that (the company) considers to be trade secrets and outside the scope of Tan’s employment,” the affidavit says.

A LinkedIn profile lists a Hongjin Tan whose background matches descriptions in the affidavit and states he was a staff scientist at the Phillips 66 Research Center in Bartlesville, about 41 miles (66 kilometers) north of Tulsa.

A spokeswoman for Phillips 66, Melissa Ory, said in an email to The Associated Press that the Houston-based company “is cooperating with the FBI on an ongoing investigation involving a former employee at our Bartlesville location.” Ory declined to discuss additional details.

Court records show Tan made an initial appearance before a federal magistrate on Thursday and remains in custody. A preliminary and detention hearing for Tan is scheduled next week.