Havana (CNN) A Cuban government investigator looking into reports of mysterious acoustic attacks on US and Canadian diplomats on the communist-run island on Monday dismissed a US government theory that microwave weapons emitting concentrated beams of radiation may have been used in the incidents.

"If you look at the alleged events, there have been reports that there are several people in a room with thick walls and thick windows and only one person was targeted. This is a kind of weapon that doesn't exist," said Dr. Mitchell Valdes-Sosa, a well-known neurologist who is part of the Cuban special task force investigating the alleged attacks. "It's science fiction, not science," he said.

"First, it was sonic weapons, now microwave. What's next, kryptonite?" the investigator said in an interview with CNN at his research center in Havana, referring to an earlier theory that sonic weapons emitting high-powered ultrasound waves could have caused the injuries.

Valdes-Sosa said researchers and investigators are working on a paper to rebut the microwave weapons theory.

Previously, the government not only denied involvement in the attacks but cast doubt on whether they actually occurred. In June, Cuba's Foreign Ministry said "political motivations" drove the United States to withdraw its embassy personnel.

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