Super Micro Computer Inc on Monday stated in a letter to customers it will review its hardware for any proof of installation of malicious chips in its motherboards as alleged in a recent media report.

A Bloomberg report on Oct.4 cited 17 unidentified sources from intelligence agencies and businesses that claimed Chinese spies had placed computer chips inside equipment used by about 30 companies.

the affected companies include Apple Inc and Amazon.com Inc and multiple U.S. government agencies, which would give Beijing secret access to internal networks, according to the report.

In the letter to customers dated Oct. 18 filed with the Securities and Exchange Commission, the company refuted the claim.

“We are confident that a recent article, alleging a malicious hardware chip was implanted during the manufacturing process of our motherboards, is wrong. “From everything we know and have seen, no malicious hardware chip has been implanted during the manufacturing of our motherboards.”

“Despite the lack of any proof that a malicious hardware chip exists, we are undertaking a complicated and time-consuming review to further address the article,” the chipmaker stated in the letter.

Bloomberg said it stood by its report and was confident of its reporting and sources.