Sri Lanka, June 28 -- All hypotheses on how the Covid-19 pandemic began remain open, the World Health Organization said on Friday (Jun 27), following an inconclusive four-year investigation that was hamstrung by crucial information being withheld.

The global catastrophe killed an estimated 20 million people, according to the WHO, while shredding economies, crippling health systems and turning people's lives upside-down.

The first cases were detected in Wuhan in China in late 2019, and understanding where the SARS-CoV-2 virus that causes Covid came from is key to preventing future pandemics.

However, a lengthy investigation launched by the UN's health agency said that pending further data, the origin of Covid and how it first spread rem...