Pressure is rising on Bloomberg over an investigative news report that claimed Chinese spies used microchips to infiltrate several major US technology companies, after executives at two other tech firms named in the report backed Apple chief executive Tim Cook in calling for a retraction. Super Micro Computer (Supermicro) chief executive Charles Liang issued a statement on Monday saying Bloomberg should retract the story as it contains “unsupported allegations” following on from Andy Jassy, chief executive of Amazon Web Services, who earlier tweeted that “reporters got played or took liberties, Bloomberg should retract". China hack report ‘will force US firms to rethink supply chains’ The executives’ remarks follow hot on the heels of similar comments from Cook last week, when the head of the world’s most-valuable technology company addressed the issue publicly for the first time. “There is no truth in their [Bloomberg’s] story about Apple,” Cook told BuzzFeed News in an interview. “They need to do the right thing and retract it.” A Bloomberg Businessweek report on October 4 cited 17 unidentified sources from intelligence agencies and businesses claiming that Chinese spies had placed computer chips inside equipment used by about 30 companies, including Apple and Amazon.com, and multiple US government agencies, which would give Beijing secret access to internal networks. San Jose, California-based Supermicro’s motherboards were at the centre of the malware chip allegations. The Bloomberg report was published at a sensitive time in US-China relations amid an escalating trade war, a push by the US to end forced technology transfers in exchange for market access and rising opposition to Beijing’s Made in China 2025 plan – which the Trump administration has seized on as an example of what it sees as unfair state intervention in China's economy. Hardware maker Supermicro had said on Monday it would review its motherboards for any proof of malware chips, but this report was quickly superseded by Liang’s statement. “Bloomberg should act responsibly and retract its unsupported allegations that malicious hardware components were implanted on our motherboards during the manufacturing process,” Liang said in the statement. “Bloomberg has not produced a single affected motherboard.” China’s defence in alleged chip hack: it’s mission impossible Jassy’s denial of Bloomberg’s claims in a tweet was also forthright. “They [Bloomberg] offered no proof, story kept changing, and showed no interest in our answers unless we could validate their theories.” Belina Tan, a spokeswoman for Bloomberg in Singapore, did not immediately return a phone call seeking comment. Bloomberg has said it stands by its report and is confident of its reporting, which was conducted for more than a year. Supermicro has said that the design complexity makes it practically impossible to insert a functional, unauthorised component onto a motherboard without it being caught by the checks in its manufacturing and assembly process. Meanwhile, security experts – including UK and US authorities such as the Department of Homeland Security – have said they had no knowledge of the attacks. The Bloomberg report also said that Apple in 2015 had found malicious chips on Supermicro motherboards and added that Amazon uncovered such chips the same year while examining servers made by Elemental Technologies, which Amazon eventually acquired. However, Apple, Amazon and Supermico have denied the allegations from the outset.