Senior Trump administration officials have pushed American spy agencies to hunt for evidence to support an unsubstantiated theory that a government laboratory in Wuhan, China, was the origin of the coronavirus outbreak, according to current and former American officials. The effort comes as President Trump escalates a public campaign to blame China for the pandemic.

Some intelligence analysts are concerned that the pressure from administration officials will distort assessments about the virus and that they could be used as a political weapon in an intensifying battle with China over a disease that has infected more than three million people across the globe.

Most intelligence agencies remain skeptical that conclusive evidence of a link to a lab can be found, and scientists who have studied the genetics of the coronavirus say that the overwhelming probability is that it leapt from animal to human in a nonlaboratory setting, as was the case with H.I.V., Ebola and SARS.