Army Gen. Mark A. Milley, the nation’s most senior military officer, told reporters at the Pentagon the initial assessments indicate the coronavirus causing the global pandemic appears to have been a “natural” event arising from animal-to-human transmission.

However, he noted published reports that the origin may have occurred as an escape from a research laboratory.

“It should be no surprise that we’ve taken a keen interest in that and we’ve had a lot of intelligence [agencies] take a hard look at that,” Gen. Milley said. “I would just say at this point it’s inconclusive although the weight of evidence seems to indicate natural. But we don’t know for certain.”

The comments by the four-star general are the first time a senior American government official publicly raised the prospect that the virus may have originated from a Chinese laboratory.

Defense Secretary Mark T. Esper, appearing with Gen. Milley, was asked if international inspectors should be stationed at Chinese laboratories in the future. Mr. Esper said it is something that will be looked at in the future as part of a “lessons learned” regarding the pandemic.

The outbreak began Dec. 1 in Wuhan and many of the first victims — but not all — were associated with a wild animal market in the city.

The market is located within three miles of a laboratory at the Wuhan Center for Disease Control and Prevention that Chinese state media has said is involved in extensive research on bat coronaviruses.

The Wuhan CDC laboratory that conducts bat virus research is rated a Level-2 security facility that generally is not equipped to handle deadly pathogens.

A second laboratory at the Wuhan Institute of Virology contains a Level-4 laboratory that is secure for handling deadly viruses and has been engaged in bat coronavirus research.

Shi Zhengli, a senior researcher at the Wuhan Institute of Virology known as the “Bat Woman” for her coronavirus work, has insisted the new virus is not related to her laboratory.

“The 2019 novel coronavirus is a punishment by nature [for] humans’ unsanitary life style,” Ms. Shi stated on WeChat last month. “I promise with my life that the virus has nothing to do with the lab.”

The comments by Gen. Milley also challenge the comments of some scientists and news media outlets that have labeled any discussion of the possible leak of the virus from a Chinese laboratory as a conspiracy theory.

The Washington Post reported on Tuesday that State Department officials had warned about poor security at the Wuhan Institute of Virology in 2018, and Secretary of State Mike Pompeo said on Tuesday that China is continuing to hold back needed information about the virus and the disease it causes.

“It is still the case that we need good data from all across the world,” Mr. Pompeo said. “And so we need every country, including the Chinese Communist Party, to share that data broadly, to be transparent. That data saves lives.”

Gen. Milley did not elaborate on the U.S. intelligence work on the coronavirus’s origins.

Chinese authorities have suggested the virus, which is over 90% similar to at least one coronavirus found in horseshoe bats, may have been passed to an animal host and then to humans at the “wet market,” as the wild animal distribution site is called.

The possibilities for an inadvertent release include someone becoming infected while conducting laboratory research on the virus, or if an infected research animal may have escaped or been taken from the laboratory by a worker.

A group of scientists who have studied the new virus reported in the journal Nature Medicine last month that the inadvertent release of the virus by Chinese researchers cannot be ruled out.

China’s government, after initially stating the coronavirus outbreak appeared to have started at a wild animal market in Wuhan, have backed off that theory.

Foreign Ministry spokesman have said determining the origin of the virus must be carried out by scientists. But after initially agreeing to provide samples of the virus for study, officials later refused to give virus samples to U.S. researchers.

In the early stages of the outbreak, China also blocked U.S. and international virus experts from visiting Wuhan during most of January to investigate the virus origin, and later delayed releasing the virus genome sequence for about a month to international researchers.

The wild animal market was also closed and the animals removed, limiting investigators’ ability to search for an origin. The market has since reopened, bringing fears that another virus outbreak could happen.