According to the Bloomberg report, the microchips, which were the size of a grain of rice, provided China with a way to remotely access the computers.
Bloomberg Businessweek reported Thursday that Chinese spies exploited vulnerabilities in the US technology supply chain to infiltrate computer networks of nearly 30 USA companies, including Amazon.com Inc., Apple Inc., a major bank and government contractors.
The Chinese foreign ministry also denied the allegations and said the country is a "resolute defender of cybersecurity".
The report said that dozens of companies may have used sabotaged servers in their data centers before the Chinese operation was detected.
The full statement, which is available here, added that Apple always inspects its servers before they are put into production and if it found anything suspicious, it would have alerted the authorities.
Representative Frank Pallone of New Jersey, the top Democrat on the House Energy and Commerce Committee, said the report "is deeply disturbing and Congress must investigate".
"There are so many inaccuracies in this article as it relates to Amazon that they're hard to count", the Seattle-based company said in its own statement.
According to Bloomberg, the spy chips were designed for motherboards - the nerve centers for computer equipment - used in data centers operated by Apple, Amazon Web Services and others.
However, Apple and Amazon have both strongly denied such a chip was found.
In what could be the most important U.S. national security story of the decade, a new report alleges that China has been installing tiny microchips, roughly the size of a grain of rice, on the motherboards of countless servers imported into the US.
"As we shared with Bloomberg BusinessWeek multiple times over the last couple months, this is untrue", Amazon said in a statement, which you can read here.
Each response appears to be chiefly concerned about the claim in Bloomberg's report that both companies learned of these Chinese intrusions and reported them to USA federal authorities while keeping the issues secret from the public.
AWS told Bloomberg it had reviewed its records related to the Elemental acquisition and "found no evidence to support claims of malicious chips or hardware modifications". It said it has never found any malicious chips, had not been informed that such chips were found by any customer, and never been contacted by government agencies on the matter.
"Seventeen individual sources, including government officials and insiders at the companies, confirmed the manipulation of hardware and other elements of the attacks", Bloomberg said in a statement.
John Bolton, who leads the National Security Council, didn't confirm whether the White House was aware of the Chinese hack before Bloomberg's report.
While the companies disputed the facts in the story, security experts noted that there is growing concern that hackers could launch cyber attacks by inserting malicious chips into hardware sold to government agencies and businesses.