A nuclear physicist and MIT professor fatally shot outside his Massachusetts residence. A retired Air Force general missing from his New Mexico home. An aerospace engineer who disappeared during a hike in Los Angeles.

These are among at least 10 individuals connected to sensitive US nuclear and aerospace research who have died or disappeared in recent years, prompting concerns whether they are connected and fueling speculation online about the possibility of nefarious activity.

The FBI now says it “is spearheading the effort to look for connections into the missing and deceased scientists,” adding that it “is working with the Department of Energy, Department of War, and with our state … and local law enforcement partners to find answers.”

Physicists have spent the last 20 years pondering an apparent discrepancy between experimental results and theoretical predictions for the magnetic properties of the muon, the electron’s heavier cousin—a mismatch that hinted at a possible fifth force. But according to a new paper published in the journal Nature, the discrepancy is due to a calculation fluke, not exciting new physics, so the Standard Model of particle physics is still holding strong.