By Kavitha Shastry

Apple and Amazon denied a report Thursday morning that Chinese spies were able to infiltrate their equipment and gain access to proprietary information and trade secrets.

According to Bloomberg, microchips were installed in data center machines during manufacturing. As many as 30 companies, including government contractors and a major bank, were affected.

The chips, from Chinese company Super Micro, have reportedly been under investigation by the U.S. since 2015. Amazon ($AMZN) and Apple ($AAPL) allegedly alerted authorities when they found errant hardware at the time, though in statements to multiple outlets, both tech companies denied they found any malicious chips.

In a statement to Bloomberg, Amazon said, "We've found no evidence to support claims of malicious chips or hardware modifications."

Apple, meanwhile, said, "We are deeply disappointed that...Bloomberg's reporters have not been open to the possibility that their sources might be wrong or misinformed. Our best guess is that they are confusing their story with a previously reported 2016 incident in which we discovered an infected driver on a single Super Micro server in one of our labs. That one-time event was determined to be accidental and not a targeted attack against Apple."

While consumer data was not compromised, the incident would be one of the biggest examples of corporate espionage to date and further exacerbates the already fragile tensions between the U.S. and China.

Last year the Trump administration blocked a takeover of Lattice Semiconductor ($LSCC) by China-backed private equity firm Canyon Bridge Capital over fears of the influence the foreign government might be able to wield over the chip maker. A $117 billion takeover of Qualcomm ($QCOM) by Singapore's Broadcom ($AVGO) was scuttled because of concerns the resulting company would be too dependent on Chinese smartphone maker Huawei. And just this week the U.S. Commerce Department extended a monitoring period on telecom company ZTE for two years. That company has been under probation for violating sanctions against Iran since May 2017.

Super Micro ($SCMI), though based in San Jose, Calif., makes most of its motherboards in China. It also denied its products had been compromised, saying in a statement to Bloomberg, “We remain unaware of any such investigation.”

It's not the first time the company has come under fire this year ー shares were suspended from trading on the Nasdaq in August for failing to meet quarterly reporting deadlines.