SuperMicro is trying to claw back its reputation after a widely disputed Bloomberg Businessweek article that said the California-based hardware company had allowed Chinese government microchips meant for spying onto their motherboards.

The company's stock tumbled by more than 40% on Oct. 4 and has still not fully recovered to levels before the article came out. On Tuesday, SuperMicro remained down 23% from levels prior to the story.

Company CEO Charles Liang said Tuesday SuperMicro used a "leading" third-party testing firm to test a "representative sample" of motherboards, including the boards depicted in the article and newer models. The testing showed the boards did not have malicious hardware added, he said. The company did not name the vendor that conducted the test, and did not respond to a request for comment on the vendor. However, Reuters reported that Nardello & Company conducted the review.

"As we have stated repeatedly since these allegations were reported, no government agency has ever informed us that it has found malicious hardware on our products; no customer has ever informed us that it found malicious hardware on our products; and we have never seen any evidence of malicious hardware on our products," he wrote.

The Businessweek article said Chinese Army-linked infiltrators put chips into motherboards – bound for U.S. companies, including Apple and Amazon – that were meant to be used for unknown spying purposes. The story also said the chips sparked a years-long investigation that is still ongoing.

SuperMicro has filed statements with the Security and Exchange Commission denying the claims.

Apple and Amazon have strongly disputed the story. Apple CEO Tim Cook said last month the piece is a "a 100% lie." Government representatives for the Department of Homeland Security, National Security Agency and Britain's National Cyber Security Centre have also either disputed the story or said they had no reason to doubt the companies.

Bloomberg has continued to stand by the story, saying of the piece that the investigation "is the result of more than a year of reporting, during which we conducted more than 100 interviews. Seventeen individual sources, including government officials and insiders at the companies, confirmed the manipulation of hardware and other elements of the attacks."

The Washington Post reported that Bloomberg is continuing to investigate the story.