The House Intelligence Committee is investigating how U.S. spy agencies examined cases of Havana syndrome, a potential challenge by Congress to their conclusions about the mysterious illnesses.
At the beginning of the Biden administration, intelligence agencies began a push to determine the causes of the anomalous health incidents, the government’s term for Havana syndrome. As a result of that work, intelligence agencies concluded that environmental causes, undiagnosed medical conditions or stress, rather than a sustained global campaign by a foreign power, had caused most of the ailments.
But the House investigation will look at the spy agencies’ analysis and the integrity of their work. The inquiry, depending on what it discovers and concludes, could reopen the debate over the causes of Havana syndrome, which quieted after the intelligence community said it was not the result of an adversarial country.
Havana syndrome is the name for a collection of debilitating symptoms — including migraines, vertigo and other ailments — first seen in diplomats and spies working at the U.S. Embassy in Cuba in 2016 and 2017. The symptoms often came after people felt pressure in their heads or heard strange sounds.
Eventually there were hundreds of reports of possible cases, creating a sense of crisis. But in recent years reports have diminished to a small number, officials said.
The House committee announced the investigation in a letter sent to Avril D. Haines, the director of national intelligence, on Thursday. In the letter, Representative Rick Crawford, Republican of Arkansas, said the inquiry would examine “allegations of improper suppression” of information related to the incidents between intelligence agencies and between the executive branch and Congress.
After the initial reports from Cuba, reports of diplomats, military personnel and C.I.A. officers experiencing similar symptoms proliferated in the ensuing years, first in China and then in other places around the world. Some former officials said they believed the ailments might have been caused by Russia or another adversarial state using an eavesdropping device or even some sort of weapon.
William J. Burns took the helm of the C.I.A. in 2021 promising to find out the cause of the ailments. He created an analytic team to examine the evidence. And the Office of the Director of National Intelligence assembled a group of experts to examine the classified and unclassified evidence.
The C.I.A. has compensated some former officers who suffered debilitating injury and has increased access to health care for those reporting symptoms. But first the C.I.A., in 2022, and then Ms. Haines’s office, the following year, concluded that it was very unlikely an adversarial state was behind the incidents.
Intelligence agencies found no intercepts implicating Russian or other spies. The lack of evidence was telling. American spy agencies had penetrated Russian military and intelligence services so thoroughly that they knew many details of the Russian invasion plan for Ukraine, but they found no evidence to support Russian involvement in episodes of Havana syndrome.
Timothy L. Barrett, an assistant director of national intelligence, said the agencies would continue to cooperate with Mr. Crawford and the committee.
Mr. Barrett said that even though most intelligence agencies concluded that it was very unlikely a foreign adversary was responsible for all the reported ailments, “that does not mean our work is done.”
“We continue to prioritize understanding such incidents, allocating resources and expertise across the government, pursuing multiple lines of inquiry and seeking information to fill the gaps we have identified,” Mr. Barrett said.
But many who have suffered from Havana Syndrome say the analytic work and investigation of the episodes have fallen short and have raised questions about it. They have pressed Congress for a more thorough review.
In the letter, Mr. Crawford referred to information provided to the committee from whistle-blowers and intelligence community officers. A spokeswoman for Mr. Crawford could not be reached for comment.
Mark S. Zaid, a lawyer who has represented some of the whistle-blowers, said the new investigation demonstrated that Congress was pushing back against the executive branch’s assertions that the syndrome “essentially does not exist.”
He said there was more for the House committee to learn from the spy agencies about the anomalous health incidents.
“There is no doubt in my mind based on the years I have represented AHI victims that the executive branch is covering up what it actually knows about these incidents, to include the cause and foreign perpetrators,” Mr. Zaid said. “We look forward to the truth finally being made public and accountability, both for the perpetrators and the U.S. Government deniers, occurring.”