It has nominated 26 experts to join the body, the Scientific Advisory Group on the Origins of Novel Pathogens (Sago).
More than a year-and-a-half since the virus was detected in the Chinese city of Wuhan, the question of how it first emerged remains unclear.
The team will consider if the virus jumped from animals to humans in Wuhan markets or leaked in a lab accident.
China has strongly refuted the second theory.
In February, a WHO team tasked with investigating Covid's origins flew to China and concluded that the virus had probably come from bats but that more work was needed.
But the WHO's director general, Dr Tedros Adhanom Ghebreyesus, later said the investigation had been hampered by a lack of data and transparency from China.
The proposed members of the Sago group include six experts who visited China as part of the previous team.
Aside from coronavirus, Sago will also look into the origins of other high-risk pathogens.
"Understanding where new pathogens come from is essential for preventing future outbreaks," said Dr Tedros said.
In a joint editorial in the journal Science, Dr Tedros and other WHO officials said "a lab accident cannot be ruled out".