Cuban officials investigating U.S. complaints of attacks on diplomats in Havana said talk of acoustic strikes was “science fiction” and they accused Washington of “slander” while refusing to cooperate fully with Cuba’s enquiry.

President Donald Trump said last week that he believed Havana was responsible for 24 diplomats being harmed. Earlier in October, Washington expelled 15 Cuban diplomats and recalled more than half the U.S. diplomatic personnel from Havana.

Although Cuban Foreign Minister Bruno Rodriguez had denounced the expulsions as “unjustified” and accused the United States of insufficient cooperation, three Cuban Interior Ministry officials and a doctor heading the inquiry provided more details in an interview on Sunday in Havana.

Cuba had deployed about 2,000 experts, from criminologists to audiologists and mathematicians, to investigate the incidents after it became aware of them in February, the officials said.

The probe has not ended, but so far, it had failed to uncover any evidence to corroborate allegations of attacks that the United States says have caused hearing loss, dizziness, fatigue and cognitive issues in diplomatic personnel while based on the Communist Party-ruled island.

“Our main concern at this moment are the accusations being made by the U.S. government and we are focused on that because this is a slander,” said Coronel Ramiro Ramirez, responsible for the security of diplomats in Cuba. There was no immediate comment from the White House or the U.S. State Department.

U.S. media outlets have cited Washington officials as raising the possibility that sonic weapons were used to harm the diplomats. However, Cuban investigators said the Caribbean country did not possess such weapons and denied they could even have been used by third parties without affecting the health of others or attracting attention.

“It’s impossible. We are talking about science fiction,” said Lieutenant Colonel Jose Alazo, an expert in the criminal investigation unit of the Interior Ministry. “From a technical point of view, that argument is unsustainable.”

The investigators said the United States had neither allowed access to the people it said had been harmed nor the houses where they reported the attacks took place so their team has instead studied the surrounding areas and interviewed neighbors. They have also evaluated 14 recordings of noises supplied as evidence by the United States and concluded they did not contain anything damaging.

“We have not been able to prove the incident exists, nor have we been able to prove the sounds we have analyzed damage human health,” said Lieutenant Colonel Roberto Hernandez, another investigator in the Interior Ministry.