Shares in Chinese tech giants Lenovo and ZTE have fallen sharply after a media report that Beijing had inserted spying devices into US computers.
Unnamed US national security officials, quoted by Bloomberg, said microchips were found in gadgets used by US government agencies.
Lenovo's shares fell more than 15%, while ZTE lost more than 10%.
Lenovo said it did not source parts from Super Micro, the firm at the centre of the allegations.
ZTE has declined to comment.
According to the report, Super Micro is said to have supplied servers that allegedly contained the malicious hardware.
Tiny chips on its server circuit boards had been used to siphon off data, the news agency said.
Super Micro has rejected Bloomberg's claims, calling them "untrue".
Apple and Amazon have also denied that their computer systems were among those reportedly containing the devices.
ZTE is one of China's leading state-owned companies and has long laboured under suspicions that the use of its equipment and services poses a security threat to Western nations.
In July, Washington lifted an order that blocked ZTE from doing business with US companies.
Lenovo is the world's biggest maker of desktop computers, having bought IBM's loss-making PC unit in 2005.
In 2014, it acquired another chunk of IBM, snapping up its low-end server business.