The National Institutes of Health said on Wednesday that a nonprofit group under fire from some Congressional Republicans for its research collaborations in China had failed to promptly report findings from studies on how well bat coronaviruses grow in mice.

In a letter to Representative James Comer, Republican of Kentucky, the N.I.H. said that the group, EcoHealth Alliance, had five days to submit all unpublished data from work conducted under a multiyear grant it was given in 2014 for the research. The organization’s grant was canceled in 2020 under President Trump’s administration during his feud with China over the origins of the coronavirus.

In recent months, N.I.H. officials have rejected claims — sometimes in heated exchanges with Congressional Republicans — that coronaviruses studied with federal funding might have produced the pandemic. Dr. Francis Collins, the director of the N.I.H., released a statement Wednesday night reiterating that rebuttal.

“Naturally occurring bat coronaviruses studied under the N.I.H. grant are genetically far distant from SARS-CoV-2 and could not possibly have caused the Covid-19 pandemic,” he said in the statement. “Any claims to the contrary are demonstrably false.”