WASHINGTON – The Trump administration dismissed media reports on Tuesday that Russia was involved in mysterious “attacks” against some U.S. government personnel in Cuba and China.

“We have seen a firestorm of reports out there today assigning blame to the Russian government,” with those reports attributed to unnamed sources, State Department spokesperson Heather Nauert told reporters on Tuesday. “I would caution you all to be very skeptical of those statements.”

She said the State Department is still investigating the attacks on U.S. State Department employees in Cuba but has not reached any conclusions yet.

"There is no known cause, no known individual or group believed to be responsible," she said. "The investigation is ongoing. We have not assigned any blame.”

“We still consider it be a health attack,” she added.

NBC News reported Tuesday that U.S. intelligence agencies suspect Russia of carrying out the bizarre series of attacks that led to brain injuries for U.S. personnel in Cuba and China. The NBC story said the agencies have evidence from communications intercepts collected during an ongoing investigation by the FBI, the CIA and other U.S. agencies.

In Cuba, U.S. staff reported hearing weird, loud sounds along with feelings of changes in air pressure in their homes owned and maintained by the Cuban government as well as hotel rooms. Although there had been no history of head trauma, the symptoms reported were consistent with brain injury. The diplomats described the sounds as “buzzing, grinding metal, piercing squeals and humming.”

The State Department created an expert panel in July 2017 to look into the matter. In its initial findings, the panel said the symptoms were most likely related to "neurotrauma from a non-natural source," and the department recommended further investigation.

The University of Pennsylvania’s Center for Brain Injury and Repair was selected to coordinate the evaluation, treatment and rehabilitation of the patients. Whatever the cause, the Havana patients “experienced persisting disability of a significant nature,” the University of Pennsylvania team found.

In China last month, Secretary of State Mike Pompeo said a U.S. government employee stationed in Guangzhou had reported "abnormal sensations of sound and pressure" suggesting a mild brain injury. Pompeo said the medical indications were "very similar" and "entirely consistent" to those reported by American diplomats posted in Havana.

In response to the incidents in Cuba, the State Department initially reduced the number of workers in Havana. But last March made the sharp reductions permanent, citing health concerns. State Department officials have told Congress that 26 embassy workers in Cuba were affected by the mysterious health incidents since it was first discovered in December 2016. The one employee in China found to have similar symptoms became known last May.

The Cuban government has denied there were responsible for any attacks and strongly rejected any allegations of wrongdoing.