In a report required by Congress, the Office of the Director of National Intelligence said it remains unable to pinpoint the pandemic’s origins, with spy agencies divided on whether the virus passed to humans via an infected animal or a laboratory accident. The report is a summary of findings by major U.S. intelligence agencies.

The reporta cknowledged publicly for the first time the assessment of the Federal Bureau of Investigation and Energy Department that a “laboratory-related incident” was most likely responsible for the pandemic that has killed nearly seven million people worldwide, while other agencies believe natural infection was the cause. The Central Intelligence Agency and another unnamed agency say they are unable to pinpoint the cause, the report said.

Covid-19’s origins increasingly have become a politically and scientifically volatile issue following revelations about research and biosafety practices at the Chinese lab, the Wuhan Institute of Virology, and the failure to identify animals that might be responsible for the pandemic more than three years after it began.

In March, President Biden signed a law passed by Congress requiring his administration to declassify within 90 days information related to the pandemic’s origins, including any links between the Wuhan lab and the pandemic. The legislation was passed after The Wall Street Journal reported that the Energy Department had changed its assessment to conclude, with low confidence, that the pandemic likely arose from a laboratory leak.

Friday’s 10-page declassified report said the Wuhan lab, also known as the WIV, at times collaborated with China’s People’s Liberation Army on viral research, including on coronaviruses. But, it said, that work included “no known viruses that could plausibly be a progenitor of SARS-CoV-2,” the virus that causes Covid.

Researchers at the WIV “probably did not use adequate biosafety precautions at least some of the time before the pandemic” in handling coronaviruses like those that cause Covid, “increasing the risk of accidental exposure to viruses,” the declassified report said. But, it added, “We do not know of a specific biosafety incident at the WIV that spurred the pandemic.”

Three researchers at the Wuhan institute fell ill in November 2019, at the pandemic’s outset, with symptoms consistent with either Covid or seasonal flulike illnesses. The Journal this week reported the names of the three, which included a prominent scientist who worked on coronavirus projects funded by the U.S. government.

The new report said U.S. spy agencies “assess that this information neither supports nor refutes either hypothesis of the pandemic’s origins because the researchers’ symptoms could have been caused by a number of diseases and some of the symptoms were not consistent with COVID-19.”

Write to Warren P. Strobel at Warren.Strobel@wsj.com and Michael R. Gordon at michael.gordon@wsj.com