Federal agencies are investigating at least two possible incidents on US soil, including one near the White House in November of last year, that appear similar to mysterious, invisible attacks that have led to debilitating symptoms for dozens of US personnel abroad. Multiple sources familiar with the matter tell CNN that while the Pentagon and other agencies probing the matter have reached no clear conclusions on what happened, the fact that such an attack might have taken place so close to the White House is particularly alarming. Defense officials briefed lawmakers on the Senate and House Armed Services Committees on the matter earlier this month, including on the incident near the White House. That incident, which occurred near the Ellipse, the large oval lawn on the south side of the White House, sickened one National Security Council official, according to multiple current and former US officials and sources familiar with the matter. In a separate 2019 episode, a White House official reported a similar attack while walking her dog in a Virginia suburb just outside Washington, GQ reported last year. Those sickened reported similar symptoms to CIA and State Department personnel impacted overseas, and officials quickly began to investigate the incident as a possible “Havana syndrome” attack. That name refers to unexplained symptoms that US personnel in Cuba began experiencing in late 2016 – a varying set of complaints that includes ear popping, vertigo, pounding headaches and nausea, sometimes accompanied by an unidentified “piercing directional noise.” Rumors have long swirled around Washington about similar incidents within the United States. While the recent episodes around Washington appear similar to the previous apparent attacks affecting diplomats, CIA officers and other US personnel serving in Cuba, Russia and China, investigators have not determined whether the puzzling incidents at home are connected to those that have occurred abroad or who may be behind them, sources tell CNN. Defense officials who briefed lawmakers said it was possible Russia was behind the attacks, but they did not have enough information to say for sure. Another former US official involved in the investigation at the time said China was also among the suspects. The US has struggled to understand these attacks since 2016 and 2017, when diplomatic and intelligence personnel in Cuba first began reporting alarming symptoms that seemed to appear out of the blue. Intelligence and defense officials have been reluctant to speak publicly about the strange incidents, and some who were impacted have complained publicly that the CIA did not take the matter seriously enough, at least initially. The attacks eventually led to a dramatic drawdown of staff at the outpost in Havana under the Trump administration. Personnel in Russia and China reported similar, unexplained incidents. 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 ‘bureaucratic power play’ Another mystery surrounding “Havana syndrome” is how the US government is confronting the problem. Among those investigating the mysterious pattern of possible attacks are the CIA, the State Department and the Defense Department. Near the end of the Trump administration, the Pentagon sought to take the lead out of perceived frustration that other agencies were not doing enough to address the issue. “I knew CIA and Department of State were not taking this sh*t seriously and we wanted to shame them into it by establishing our task force,” Chris Miller, who was acting defense secretary at the time, told CNN last week. Pentagon leaders set up the task force to track reports of such symptoms hitting Defense Department personnel overseas, an effort that Miller said was intended in part as a “bureaucratic power play” to force CIA and State to take the problem more seriously in their own personnel. Miller said he began to see reports of these mysterious symptoms as a higher priority in December, after interviewing an alleged victim with extensive combat experience. “When this officer came in and I knew his background and he explained in an extraordinarily detailed but more military style that I could understand, I was like this is actually for real,” Miller said. “This kid had been in combat a bunch and he knew.” The CIA began its task force in December 2020, and expanded its efforts under new Director William Burns, who vowed during his confirmation hearings to review the evidence on the alleged attacks on CIA personnel overseas, which have long been publicly reported. The State Department named a senior official to lead the department’s response to the “Havana syndrome” attacks in March. The Defense Department’s effort is thought to be among the most robust, potentially explaining why a defense official, rather than the intelligence community or the FBI, briefed lawmakers on the incident at the Ellipse, even though it took place on US soil. Miller tapped Griffin Decker, a career civil servant from US Special Operations Command, to run the effort. Decker would track and verify reports in the military of what by then had become known informally as “Havana syndrome.” Miller says Griffin would report a new case to him “every couple of weeks,” although he cautioned that they were on the lookout for false reporting, psychosomatic episodes or hypochondria. Some of the cases they tracked included the children and dependents of Defense Department personnel overseas, Miller said. Director of National Intelligence Avril Haines was asked about CNN’s reporting by Sen. Jeanne Shaheen, a New Hampshire Democrat, at a Senate Armed Services Committee hearing on Thursday. Haines did not discuss the specifics but called the issue of the mysterious attacks “critically important” and added, “across the intelligence community, frankly, leaders are focused on this issue.” Haines also defended the classification of information related to the attacks but said members of Congress “should certainly have access to the classified information.” A White House spokesperson said in a statement, “The White House is working closely with departments and agencies to address unexplained health incidents and ensure the safety and security of Americans serving around the world. Given that we are still evaluating reported incidents and that we need to protect the privacy of individuals reporting incidents, we cannot provide or confirm specific details at this time.” Difficult to determine cause of symptoms Decker and Jennifer Walsh, who was the acting under secretary of defense for policy, briefed House and Senate lawmakers over the last two weeks on the possible attacks, two sources familiar with the briefings told CNN. Politico first reported on the committee briefings. In one incident that was investigated, Marines on a remote base in Syria developed flu-like symptoms shortly after a Russian helicopter flew over the base – raising immediate concerns that it could be one of these strange attacks. But “it was quickly traced, where they had bad food and where no one else on the base had the same symptoms,” said one former US official with knowledge of the incident. It was also determined by a defense physician that the symptoms had begun prior to the Russia patrol, a defense official told CNN. The Syria episode highlights the difficulties that US officials face in trying to pin down what is and isn’t an attack. The symptoms often vary, and officials still have no clear sense of how the unknown adversary is doing what it’s doing. At least one former US official with knowledge of the matter said that 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. Another US defense official confirmed that the Pentagon’s investigation is ongoing. The official would offer no details, but said, “We would not still be looking at this if we didn’t have equities in it.” “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.” A March report from the National Academy of Sciences found that “directed, pulsed radiofrequency energy” was the most likely cause of the strange set of symptoms. While the report was carefully written not to overstate its findings, it offered some of the clearest public evidence to date that the incidents could be attacks, attributing the afflictions to “pulsed” or “directed” energy. Some personnel have been seriously injured from the alleged attacks, with at least one career CIA officer forced to retire last year and diagnosed with a traumatic brain injury. This story has been updated with comments from the White House and also the Director of National Intelligence.