Some 2,000 investigators and scientists were assigned to uncover the mystery behind alleged sonic attacks against U.S. diplomats in Havana. Three hundred people were interviewed. Air and soil samples were analyzed. Hotel rooms and home surroundings were scoured for evidence.

Nothing was found — at least that’s what high-ranking Cuban military officials and investigators told NBC and Reuters this week in separate interviews.

Cuban officials in charge of the investigation in Havana emphatically denied that their government was involved in the attacks and dismissed the idea as “slander.”

“It is impossible. We’re talking about science fiction,” Lt. Col. Jose Alazo, head of the Interior Ministry’s criminal investigation unit, told Reuters.

“Cuba has never produced these type of weapons,” he said. “We’ve been unable to find anything to prove this situation exists or ever existed,” Alazo said.

Most of those who spoke to the foreign press are high-ranking officials at the Interior Ministry, the same body that carries out surveillance of foreign diplomats on the island. In fact, one of the officials interviewed is Col. Ramiro Ramírez, who is responsible for the security of diplomats in Cuba.

“Our main concern at the moment is the accusations the U.S. government is making and we are focusing on that because this is a slander,” he said.

The first attacks were reported in November and the last one in August. A former intelligence official, who defected to the United States in 1989, told el Nuevo Herald he does not believe the Cuban government accounts.