The World Health Organization said that China has blocked the arrival of a team investigating the origins of the coronavirus pandemic, in a rare rebuke from the UN agency. WHO Director-General Tedros Adhanom Ghebreyesus said two scientists on the United Nations team had already left their home countries for Wuhan when they were told that Chinese officials had not approved the necessary permissions to enter the country. The arrangements had been jointly agreed with China in advance. "I am very disappointed with this news," Tedros told a news conference in Geneva on Tuesday. "I have been in contact with senior Chinese officials and I have once again made clear that the mission is a priority for WHO and the international team." Tedros said WHO was "eager to get the mission underway as soon as possible" and that he had been given assurances that Beijing was speeding up the internal procedure for "the earliest possible deployment." Dr. Michael Ryan, executive director of WHO's health emergencies program said there was an issue with visas and one team member had already returned home. The other was waiting in transit in a third country. WHO officials have long been negotiating with Beijing to allow a team of global scientists access to key sites to investigate the origin of the virus — first detected in Wuhan in December 2019 — and its likely jump from an unidentified host species to humans. In May, WHO agreed to hold an inquiry into the global response to the pandemic after more than 100 countries signed a resolution calling for an independent probe. Ryan said the team hoped it was "just a logistical and bureaucratic issue" that can be resolved in "good faith in the coming hours and recommence the deployment of the team as soon as possible." In a press briefing Wednesday, spokesperson for China's Ministry of Foreign Affairs, Hua Chunying, said China had "always held an open, transparent and responsible attitude" on tracing the origin of the virus. Hua said that China had previously welcomed WHO experts into the country and said that the UN investigation team and Chinese experts have "maintained frequent interactions" including four video meetings between October and December. "In order to ensure that the international expert group that comes to China can work smoothly, it is needed to fulfill the necessary procedures and make relevant specific arrangements. The two sides are still negotiating about this," said Hua. Marion Koopmans, a Dutch virologist who heads the Erasmus Medical Centre's Department of Viroscience in Rotterdam and is part of the investigation team heading to China, said that they were "ready to go." Koopmans said that they have been told nothing is off limits while in China and said the team will be working in collaboration with their Chinese colleagues "looking at the data, talking to people with expertise, and concluding from what's been done, and what can be built on." She said it was important to understand the origins of how the virus made the leap to humans because there is "no country that doesn't have the risk of disease emergence. It's something we need to understand, so the whole world can prepare." "We really need to have patience and not judge. It's meticulous work, it will take time," Koopmans said. — Courtesy CNN