WASHINGTON DC - Federal authorities are looking into the possible occurrences of at least two mysterious and seemingly invisible attacks on US soil, including one near the White House in November of last year, according to a recent CNN report.

The news outlet references its sources as it explains why the attacks are described as mysterious in nature and "invisible," stating, "The Pentagon and other agencies probing the matter have reached no clear conclusions on what happened." 

Defense officials took data related to the incidents to lawmakers on the Senate and House Armed Services Committees earlier this month.

The officials explained what happened in the alleged incident near White House. They said it unfolded near the Ellipse, which is the large oval lawn on the south side of the White House. Apparently, a National Security Council official was suddenly ill. 

In a separate 2019 incident, a White House official reported a similar occurrence while walking her dog in a Virginia suburb just outside Washington, GQ reported last year.

In both cases, the officials who were sickened reported similar symptoms to those experienced by CIA and State Department personnel who were impacted overseas by something known as a, "Havana syndrome" attack.

CNN says "Havana syndrome" attack is a label given to unexplained symptoms that US personnel in Cuba began experiencing in 2016, it involves a varying set of complaints that include ear popping, vertigo, pounding headaches and nausea, sometimes accompanied by an unidentified "piercing directional noise."

CIA officers and other personnel who serve in Cuba, Russia, and China have been reported victims of Havana syndrome attack. 

The news outlet goes on to say that for quite some time now, a number of officials in Washington have quietly mentioned episodes of similar situations occurring on U.S. soil.

These recent incidents of possible attacks around Washington are concerning to defense officials who told lawmakers they believe Russia may be responsible for. However, officials were quick to add that they do not have sufficient data to confirm Russia's involvement.

US officials have had difficulty understanding the nature of these attacks since they began in 2016, CNN notes, and federal officials have been hesitant to speak about them publicly. 

But the tendency to remain mum on the matter was in no way indicative its gravity.

According to CNN, during the Trump administration, the attacks eventually led to a significant reduction in staff at the outpost in Havana.

Federal investigators are now ramping up efforts to understand exactly what's been happening in each of the seemingly related events.

Though they have yet to find any definite conclusions, progress has been made in theorizing what may have caused the symptoms reported by those involved.

In this regard, CNN states, "Though there's no consensus as to what causes the symptoms, one State Department-sponsored study found they likely were the result of microwave energy attacks."

A March report from the National Academy of Sciences said that "directed, pulsed radiofrequency energy" could be the cause of the symptoms. The report was carefully written so as not to overstate its findings, but it offered some of the clearest public evidence to date that the incidents could be attacks, attributing the afflictions to "pulsed" or "directed" energy.

It's also of note that least one former US official with knowledge of the matter said investigators still haven't completely ruled out the possibility that the symptoms are caused by some kind of naturally occurring phenomenon, rather than a weapon.

In any case, a US defense official confirmed that the Pentagon's investigation into the incidents remains ongoing. 

"There is nothing that the Secretary of Defense takes more seriously that the safety, health and welfare of our personnel serving around the globe in defense of our values and freedoms," Pentagon press secretary John Kirby said in a statement. "Any concerns on issues that call that into question are thoroughly reviewed, and the appropriate actions are taken to mitigate risks to our personnel."