Regulators say there is no evidence that the milk poses a danger or that a live virus is present
US President Donald Trump said last week that his government was trying to determine whether the virus emanated from a lab in Wuhan in central China.
"All available evidence suggests the virus has an animal origin and is not manipulated or constructed virus in a lab or somewhere else," WHO spokeswoman Fadela Chaib told a Geneva news briefing. "It is probable, likely that the virus is of animal origin."
It was not clear how the virus had jumped the species barrier to humans but there had "certainly" been an intermediate animal host, she added.