It was supposed to be the day that a team of 15 scientists from the World Health Organization was finally able to begin its investigation into the origins of the coronavirus in China. But Chinese officials have again managed to impede the probe by throwing up last-minute obstacles. In a Twitter post, the WHO said two of its scientists were blocked from entry because they tested positive for coronavirus antibodies. The 13 others were allowed to enter China, but they must now undergo two weeks of quarantine in Wuhan, where the virus was first recorded. The Chinese government has repeatedly found ways to delay the arrival of the team—last week, visa issues prevented them from entering the country. On the same day the scientists arrived, mainland China confirmed its first recorded COVID-19 death in eight months.