UNIVERSITY CITY (WPVI) -- A new study is out on the injuries some American diplomats suffered in Cuba.
However, the mystery continues on what caused them.
Researchers at the University of Pennsylvania say the 21 diplomats suffered classic signs of a concussion - headaches, fatigue , problems with vision, memory, concentration, and moods.
But they never had blows to the head.
Virtually all those affected reported strange sounds in their homes or hotel rooms, such as loud buzzing or grinding metal.
Yet the F-B-I and Penn ruled out sonic attacks, because those audible sounds wouldn't cause that damage.
They feel the sound may have been a side effect of the attack.
The Penn team says there's much more to learn about the incidents.
But they want doctors to be on watch for similar cases.
Diplomats in Cuba suffered brain injuries, without blow to head
Univ. of Pa. researchers still baffled on how 21 Americans were hurt
More TOP STORIES News