Another American journalist has come forward to say that multiple sources in the military and intelligence communities have told him that the United States is in possession of at least a dozen spacecraft of extraterrestrial origin and has withheld that information from the public and members of Congress for years.

Michael Shellenberger, who writes on Substack and recently gained notoriety for testifying to Congress about the so-called Twitter Files, reports that his sources confirmed the substance of astonishing allegations from an intelligence community whistleblower that surfaced earlier this week in the Debrief and on NewsNation. The whistleblower, David Grusch, suggested that the United States has possessed alien technology for decades.

A spokeswoman for the Pentagon’s new UFO watchdog, the All-domain Anomaly Resolution Office, Sue Gough, refuted Mr. Grusch’s allegations after the reports circulated. “To date, AARO has not discovered any verifiable information to substantiate claims that any programs regarding the possession or reverse-engineering of extraterrestrial materials have existed in the past or exist currently,” she said in a statement.

The denials from the Pentagon prompted anger and frustration among Mr. Shellenberger’s sources because it illustrates the infighting within the intelligence community over the topic of what are now called in bureaucratic circles “unidentified aerial phenomena.”

“The denials coming out of Susan Gough and the Pentagon are specifically chosen to use AARO as the source of information when Grusch has already addressed that AARO didn’t have access” to the classified material about the program. “And so, of course, they didn’t discover anything.”

Mr. Grusch’s credibility has been questioned in some circles because, while he has presented material backing up his claims to the Intelligence Community Inspector General, Thomas Monheim, he has not produced any photographs of the so-called alien spacecraft to reporters repeating his allegations. Mr. Schellenberger notes, however, that the Department of Defense letter authorizing Mr. Grusch to speak to the press specifically precludes him from sharing any “photograph, picture, exhibit, caption or other supplemental material” on the topic.

Some of the same sources that have been feeding Mr. Grusch information also reportedly spoke to Mr. Shellenberger. They said the U.S. government is in possession of at least 12 to 15 nonhuman aircraft. “There were at least four morphologies, different structures,” one of those sources said. “Six were in good shape; six were not in good shape. There were cases where the craft landed, and the occupants left the craft unoccupied. There have been high-level people, including generals, who have placed their hand on the craft, and I would have no reason to disbelieve them.”

The sources told Mr. Shellenberger that they felt compelled to speak out in order to buttress Mr. Grusch’s claims. All did so anonymously because they are subject to “non-disclosure agreements or secrecy agreements that we are supposed to take to the grave,” one said.

“I briefed the Senate intelligence committee, the Senate Armed Services Committee, and ARRO, and so that information is out there,” another source said. “What Grusch did was the first giant step to get the information out.”