Data center equipment run by Amazon Web Services and Apple may have been subject to surveillance from the Chinese government via a tiny microchip inserted during the equipment manufacturing process, according to a Bloomberg BusinessWeek report on Thursday. The claims in the report have been strongly disputed by the technology giants.

The chips, which Bloomberg said have been the subject of a top secret U.S. government investigation starting in 2015, were used for gathering intellectual property and trade secrets from American companies and may have been introduced by Super Micro, a Silicon Valley company that manufacturers parts for servers in China.

Apple, AWS and Super Micro dispute the report. Apple said it did not find the chips as asserted by BusinessWeek — which cited anonymous government and corporate sources. Super Micro reportedly denied that it introduced the chips during the manufacturing.

Shares of Super Micro plummeted more than 40 percent following the report. Trading of the small server company's common stock on the Nasdaq was suspended on Aug. 23 after repeatedly missing SEC filing deadlines. Super Micro shares now trade on over-the-counter markets.

Apple shares edged 1 percent lower in Thursday trading, while Amazon fell about 1.5 percent.