Those who still suspect the outbreak in China may have been caused by a lab leak or accident are pressing for an independent investigation.

A small group of scientists and others who believe the novel coronavirus that spawned the pandemic could have originated from a lab leak or accident is calling for an inquiry independent of the World Health Organization’s team of independent experts sent to China last month.

While many scientists involved in researching the origins of the virus continue to assert that the SARS-CoV-2 pandemic almost certainly began in a leap from bats to an intermediate animal to humans, other theories persist and have gained new visibility with the W.H.O.-led team of experts’ visit to China. Officials with the W.H.O. have said in recent interviews that it was “extremely unlikely” but not impossible that the spread of the virus was linked to some lab accident.