Supermicro has sent a letter to its customers saying that it has found no evidence of malicious chips on its motherboards. The company asked third-party company Nardello & Co. to audit Supermicro’s hardware.

On October 4, a Bloomberg report claimed that China’s spies managed to conceal tiny malicious chips on Supermicro motherboards. Those chips would then end up in data centers operated by Supermicro customers, such as Amazon and Apple.

The article quickly became controversial as nobody could corroborate the story. Both Apple and Amazon issued multiple rebuttals, putting their own reputation on the line.

Supermicro instantly denied the report and hired an outside investigations firm. Many customers also conducted multiple audits. Nardello tested motherboards that are currently in production as well as models that have been sold to Apple and Amazon in the past. The firm also looked at suspicious software activities.

Today, Nardello concluded that there’s no evidence of malicious hardware on the motherboards.

“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,” Supermicro executives wrote in the letter.

Bloomberg hasn’t published any retraction or irrefutable proof since then. But the damage is done and Supermicro shares took a nosedive, dropping more than 41 percent right after the initial report was published.