A team of scientists investigating the origins of Covid in China have been given access all areas passes to discover how the pandemic started.
The World Health Organisation (WHO) experts are in Wuhan to to work out what caused the virus that has killed more than two million people in 12 months.
The team are set to announce their details findings later this week in an eagerly awaited report.
British zoologist Peter Daszak told CNN his team of investigators had submitted a list of places to visit and people to speak to, receiving no opposition from the Chinese authorities, the Daily Mirror reported.
He added that evidence has been found about the virus' origins and is being "pieced together".
He said: "We are not running rogue here, we are talking to our hosts. We are in a foreign country, we are guests of China right now.
"This is a good, collaborative, scientific approach to understanding more about the origins of Covid."
When asked if it was possible that virus was engineered from within Wuhan's Institute of Virology lab, he replied: "There's no evidence of that at all - but it is something that we talked about with people at Wuhan lab.
"We got really good and honest and frank, informative answers to because they themselves brought this up - conspiracies around lab leaks that they feel strongly have no grounds.
"What we are trying to do right now is keep an open mind to every possibility.
“It was good to see the lab and you confirm your suspicions - it is an incredibly well-built, well-designed and well-managed lab."
It is hoped the WHO investigation will shed light on the origins of Covid and how the virus, believed to have began at a live food market in the city, came to devastate the world over the past 12 months.
He added: "We are still piecing together evidence, so we are looking at the animal evidence, what was sold on the market and where did it come from, what types of animals are they."
Mr Daszak's team has now finished visiting the sites it wanted to see site visits and will spend the next few days trawling through data and consulting with Chinese experts.
It will then present a summary of findings at a news briefing before they leave the city on Wednesday.
Areas being looked at by the WHO experts include the first cases, the link with animals and the unproven theory that the virus was brought into China on packaging from imported frozen food.
Meanwhile, Dr David Nabarro said the WHO's investigation into how the pandemic started was getting "exemplary co-operation" from Chinese authorities.
He told Sky News: "All the sites that WHO people wanted to visit are being visited, there is an openness for all kinds of communication to take place.
"But it's early days, this is detective work. We're anticipating this will take quite a lot longer."
Asked if he could rule out the theory that the virus escaped from a laboratory in Wuhan, he said: "The thing about theories is you have to have them as a way to set up the reason why things might be occurring in a particular way.
"I can't rule anything out and I know the team on the spot, as well as those they're talking to in China, they're not ruling anything out either.
"All options are on the table and everything will be looked at."
China has always strongly denied the possibility of a leak from the lab.
It has promoted unproven theories that the virus may have originated elsewhere before being brought to Wuhan, including on imported frozen food packaging.
