Three US intelligence officials and two others briefed on the probe told NBC News that evidence from communication intercepts indicates Russia is likely behind the attacks. However, the report added the evidence is not conclusive enough for Washington to formally blame Moscow for the incidents.
READ MORE: US State Dept. Warns Americans About Possible Sonic Attacks in Cuba
As State Department spokesperson told Sputnik on Tuesday, The United States has not determined yet who is responsible for sonic attacks on American diplomats in Cuba and China as the investigation into the incidents is still underway.
"The investigation is ongoing. We have made no determination on who or what is responsible for the health attacks," the spokesperson said.
In August of 2017, the State Department said nearly two dozen diplomats working at its embassy in Cuba were affected by an incident involving a mysterious audio device. Some of the diplomats suffered permanent hearing loss and possible brain injuries due to a sonic weapon.
US officials are still unsure what type of device caused problems for the diplomats, however, media reports indicate scientists have come up with multiple theories, ranging from weaponized electromagnetic pulses to accidental feedback from improperly installed listening devices.
