Tesla Inc TSLA.O Chief Executive Officer Elon Musk questioned the accuracy of COVID-19 tests on Thursday after claiming that results showed he tested positive twice and then negative twice all on the same day. “Something extremely bogus is going on. Was tested for covid four times today. Two tests came back negative, two came back positive. Same machine, same test, same nurse. Rapid antigen test from BD,” Musk said in a tweet, possibly referring to Becton Dickinson and Co’s BDX.N rapid antigen test. Musk, who took rapid antigen tests on Thursday, said he was also awaiting results from polymerase chain reaction (PCR) tests from different labs. When asked by a Twitter user if he showed any symptoms, Musk said he had symptoms of a “typical cold”. “Nothing unusual so far,” Musk added. Becton Dickinson, which is one of the major suppliers of COVID-19 antigen tests, said in September it was investigating reports from U.S. nursing homes that its rapid coronavirus testing equipment was producing false-positive results. Earlier this month, the U.S. Food and Drug Administration said it was alerting clinical laboratory staff and healthcare providers that false positive results can occur with COVID-19 antigen tests. Musk had previously criticized coronavirus-related restrictions and lockdowns, referring to those as “fascist” and an infringement on individual liberty. Becton Dickinson did not respond to a request for comment late on Thursday.