Tesla's Elon Musk tests positive -- and negative -- for virus
Elon Musk attends a forum in Hong Kong, China on Jan. 26, 2016. (Reuters/Bobby Yip)

Tesla founder Elon Musk says he has tested positive for the novel coronavirus while also testing negative, offering a skeptical view of the validity of the procedures.

In a series of tweets early Friday, Musk said he had conflicting results from rapid "antigen" tests for Covid-19 after he had "mild sniffles & cough & slight fever" in recent days.

"Something extremely bogus is going on. Was tested for covid four times today," he wrote. "Two tests came back negative, two came back positive. Same machine, same test, same nurse."

Musk, who earlier this year dismissed concerns about the pandemic and fought lockdown orders in California, said he planned to take the more accurate PCR test which must be sent to a lab for analysis.

The rapid antigen tests have gained ground in recent weeks in view of backlogs at laboratories, but they are less sensitive to small amounts of virus and more likely to deliver a false negative.

In March, Musk appeared to dismiss concerns about the pandemic, saying that "my guess is that the panic will cause more harm than the virus."

Two months later he defied lockdown orders in California to reopen the Tesla assembly plant, daring authorities to arrest him.

Musk's space company SpaceX was set to launch four astronauts to the International Space Station Saturday, for the first time since a successful crewed test flight in May.

Musk was in the control room for that mission, but NASA chief Jim Bridenstine said Friday that protocol ruled out the presence of anyone who tested positive at the Kennedy Space Center.

"When somebody tests positive for Covid here at the Kennedy Space Center, and across NASA, it is our policy for that person to quarantine and self-isolate," he said at a press conference.

"So we anticipate that that will be taking place. And, you know, we're looking to SpaceX to do any contact tracing that is appropriate."

The astronauts have been in quarantine since October 31, and Bridenstine did not want to predict whether there was a risk of postponing the launch if possible contact cases were identified.