Apple Inc. and Amazon.com Inc. denied a Bloomberg report on Thursday that their systems had been infiltrated by malicious computer chips inserted by Chinese intelligence, according to statements from the companies released by Bloomberg.

Bloomberg Businessweek cited 17 unnamed intelligence and company sources as saying that Chinese spies had placed computer chips inside equipment used by about 30 companies and multiple U.S. government agencies, which would give Beijing secret access to internal networks.

Representatives of Apple, the FBI and Department of Homeland Security could not be reached for comment. An NSA spokeswoman said she had no immediate comment.