All hypotheses are still open in the search for the origins of COVID-19, World Health Organization (WHO) Director-General Tedros Adhanom Ghebreyesus has told a briefing.
His comments come after a WHO-led mission in China said week that it was not looking further into the question of whether the virus escaped from a lab, which it considered highly unlikely.
The United States has said it will review the mission's findings.
Dr Tedros said the global health body was keeping an open mind as it continued its investigation.
"Some questions have been raised as to whether some hypotheses have been discarded," Dr Tedros said.
"Some of that work may lie outside the remit and scope of this mission.
The mission has said its main hypotheses are that the virus originated in a bat.
However, there are several possible scenarios for how it passed to humans, possibly first by infecting another species of animal.
The administration of former US president Donald Trump said it believed the virus may have escaped from a lab in the Chinese city of Wuhan.
China has strongly denied this, and says the Wuhan Institute of Virology was not studying related viruses.
Reuters
