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.