U.S. officials investigated a previously unreported experiment in Norway in which a government scientist tested a microwave device and developed neurological symptoms similar to so-called Havana syndrome, the Washington Post reported on Saturday citing people familiar with the matter.

Norway informed the CIA about the incident, prompting at least two visits by Pentagon and White House officials, the report said.

People familiar with the test said the results did not prove U.S. diplomats and spies were targeted by a foreign adversary, though they showed pulsed-energy devices can affect human biology.

The findings were surprising given the Norwegian researcher’s standing as a prominent skeptic of claims that directed-energy weapons can produce symptoms linked to anomalous health incidents, according to people familiar with the matter.

In attempting to dramatically disprove the theory by using himself as a test subject, he instead appeared to undermine his own position.

"I don’t know what possessed him to go and do this," one of the people said. "He was a bit of an eccentric."

AHIs, known as possible anomalous health incidents, are unexplained medical events, usually reported by groups of people in the same place and time, who suddenly experience symptoms like dizziness, headaches, nausea, ear pain, ringing in the ears, pressure sensations, or cognitive "fog."

They are best known to the public because of "Havana syndrome," the nickname given to a wave of reports starting in 2016 involving U.S. diplomats and intelligence personnel overseas.

The U.S. government has confirmed hundreds of reported incidents among U.S. diplomats, intelligence officers, military personnel, and family members since 2016.

Paul Friedrichs, a retired military surgeon and Air Force general who oversaw biological threats on the White House National Security Council under President Joe Biden, told the Post he thinks "there’s compelling evidence that we should be concerned about the ability to build a directed-energy weapon that can cause a variety of risk to humans."

The report follows reporting that Homeland Security Investigations, using War Department funding, spent more than a year testing a device purchased through an undercover operation.

The device is believed to emit pulsed radiofrequency energy, a theory long cited by some scientists as a possible explanation for Havana syndrome symptoms.

Sources said the device contains Russian components and can fit inside a backpack.

Medical findings have been mixed. Some affected individuals were diagnosed with organic brain injuries despite scans showing no visible structural damage.