A collection of World Health Organization experts were late last year granted access to visit China to explore the origins of the coronavirus.
It was hailed as a massive step forward in understanding how Covid-19 transferred from animals to humans.
However, the group of scientists say it has been blocked by China from entering Wuhan, which is largely regarded as the epicentre of the pandemic.
World Health Organisation Director-General Tedros Adhanom Ghebreyesus has slammed the Asian superpower and accused it of trying to undermine the independent investigation into the coronavirus.
"I'm very disappointed with this news given that two members had already begun their journey and others were not able to travel at the last minute," he told a news conference in Geneva, according to the Sydney Morning Herald.
"I have been in contact with senior Chinese officials and I have once again made it clear the mission is a priority for WHO and the international team. We're eager to get the mission underway as soon as possible."
A WHO official claims some members of the research mission haven't been issued visas to enter Wuhan.
The World Health Organization's Dr Michael Ryan said one person has been turned around at at the border while another is waiting in a different country until they get the green light.
"We trust and we hope that this is just a logistic and bureaucratic issue [and] will be resolved very quickly," Dr Ryan said.
"This is frustrating and as the Director-General has said this is disappointing. We trust in good faith we can solve these issues in coming hours and recommence the deployment of the team as urgently as possible."
Australia had pushed hard on getting an independent inquiry into the origins of the coronavirus, which has since caused sour relations with China.
However, many thought it was a big step forward when The WHO was granted permission to investigate the course of Covid-19 in the middle of December.
The crack team from The WHO was meant to consist of 10 people and they were meant to be working with Chinese scientists for four to five weeks.
Fabian Leendertz, a biologist at Germany's Robert Koch Institute, is one of the 10 and told the Associated Press it will be brilliant if they can locate the origin and source of the virus.
"It's really not about finding a guilty country," Leendertz said. "It's about trying to understand what happened and then see if based on those data, we can try to reduce the risk in the future."Featured Image Credit: PA