The U.S. military inquiry into the so-called Havana syndrome, the mysterious illness claimed by a litany of American intelligence officers, is tapping a controversial contractor: a private surveillance firm that once boasted of its ability to stalk American intelligence officers.

Documents obtained by The Intercept through a Freedom of Information Act request reveal that technology from the Virginia-based startup Anomaly 6 has been used to assist the “Anomalous Health Incidents Cross Functional Team,” the Pentagon’s official Havana syndrome investigatory task force. That group studies a cluster of strange symptoms claimed by personnel from U.S. spy agencies, the State Department, and elsewhere in the federal government.

In 2022, The Intercept revealed that Anomaly 6 had used a provocative demonstration of its surveillance prowess in a closed-door business pitch. The company, which purchases bulk cellular location data harvested from millions of unwitting smartphone users around the world, showed a potential customer that its data stores were so vast and accurate that it could pinpoint the movements of employees of both the CIA and NSA, tracking them as they commuted between their homes and their respective agencies headquarters. It was a remarkable demonstration of the advanced capabilities of private sector surveillance brokers, who lean on unscrupulous smartphone apps and advertisers that indiscriminately share and sell users’ location data.