BERLIN (AP) — The head of the World Health Organization has acknowledged it was premature to rule out a potential link between the COVID-19 pandemic and a laboratory leak.

In a rare departure from his usual deference to powerful member countries, WHO Director-General Tedros Adhanom Ghebreyesus said Thursday that getting access to raw data had been a challenge for the team that traveled to China earlier this year to investigate the source of the coronavirus.

Tedros said there had been a “premature push” to rule out the theory that the virus might have escaped from a Chinese government lab in Wuhan.

His statement undermines a WHO report which concluded that a laboratory leak was “extremely unlikely.”