American officials testifying before a special committee looking into the mysterious attacks in Cuba said that the Canadian government has withdrawn some of its personnel from its embassy there and raised the specter of whether Russia could be behind the attacks.

Speaking before a subcommittee of the United States Senate Committee on Foreign Relations, a senior aide to State Department Secretary Rex Tillerson said that the American government is not the only one that has withdrawn at least some of its staff from Cuba, and pointed to actions he says have been taken from the Canadian government.

READ MORE: Canadian officials wondered if Cuba staff imagined symptoms from mysterious attacks

“The Canadians have withdrawn some of their personnel but I think we can go into greater detail in a classified setting on that,” said Francisco Palmieri, acting assistant secretary to Tillerson when asked whether the U.S. decision to withdraw more than half of its embassy from Cuba late last year was in line with how other countries were reacting to the threat posed by the attacks.

Story continues below advertisement

Global News has reached out to Global Affairs Canada asking to confirm the statement by Palmieri that Canadian diplomatic personnel have been removed from Cuba.

While no statement has been provided, the department announced it will hold a technical briefing for media on Wednesday morning about “reported health incidents in Cuba.”

Despite meetings held between the Privy Council Office and the Cuban government last summer, the Canadian government has so far been hesitant to point the finger at the Cuban government for any responsibility it might have for the attacks.

For months, speculation has swirled over the cause of mysterious cognitive and auditory symptoms confirmed in at least five Canadians and 24 Americans posted in Havana, ranging from headaches and hearing loss to blurred eyesight, loss of balance, and loss of short-term memory.

READ MORE: Rex Tillerson says Cuba still risky despite FBI doubts over sonic attack

Victims have reported hearing a mysterious sound: a pulsing, high-pitched noise ranging from seconds to minutes in length.

Some reports have described it as a mass of crickets or a whine high enough to draw comparisons to the infamous nails-on-the-chalkboard effect.

Several victims have said the sound was so loud it woke them from sleep while others have said they are not aware of having heard a sound at all.

Story continues below advertisement

WATCH BELOW: U.S. senator says no evidence of ‘sonic attacks’ in Cuba

1:17 U.S. senator says no evidence of ‘sonic attacks’ in Cuba U.S. senator says no evidence of ‘sonic attacks’ in Cuba

The sounds were not heard in official facilities but rather in several areas where diplomats resided in the city between November 2016 and May 2017, with several further cases affecting Americans reported in August 2017, shortly before media reports of the mysterious incidents emerged.

As Global News first reported last week, Canadian officials were scratching their heads trying to figure out whether reports of symptoms in staff at the Canadian embassy were real or all in employees’ heads, and dispatched the overseas medical adviser from Health Canada to Cuba in June 2017 to meet with victims.

Emails obtained under access to information laws revealed that Global Affairs Canada had also prior to that visit arranged for a medical team from the Department of National Defence to help assess victims, and later recommended that Canadian foreign service staff posted to Cuba be given the option to opt out.

Story continues below advertisement

The department has also begun giving baseline audiometry tests to all employees and their families being posted to Cuba, something American officials said Tuesday they have also done.

2:05 Secret “sonic weapon” could be giving diplomats in Cuba brain injuries Secret “sonic weapon” could be giving diplomats in Cuba brain injuries

WATCH ABOVE: Secret “sonic weapon” could be giving diplomats in Cuba brain injuries

Todd Brown, the assistant director of diplomatic security for the U.S. State Department, was asked whether it is possible to guarantee the safety of American staff being posted to Havana, and told the committee he could not.

“I don’t think we can say categorically that they would be safe from this,” Brown said. “Not knowing what’s causing or or how it’s being done gives us very little in terms of mitigation.”

The question of what – or who – is behind the mysterious attacks has stumped doctors and diplomats since reports of symptoms began in late 2016.

Story continues below advertisement

Initially believed to involve some kind of sonic weapon because of the overlapping reports among many victims involving strange noises, a report published by the Associated Press on Monday reveals doubts among Federal Bureau of Investigation officials tasked with determining a cause.

That report by the FBI’s Operational Technology Division reportedly said there was no evidence that sound waves could harm an individual’s health, but did not examine other theories for what might be behind the attacks, some of which point the finger at Russia.

When asked about the report, Tillerson said it would not change his decision to pull the majority of American diplomatic staff out of Cuba.

“I’d be intentionally putting them back in harm’s way. Why in the world would I do that when I have no means whatsoever to protect them?” Tillerson said. “I will push back on anybody who wants to force me to do that.”

U.S. Senator Marco Rubio, who convened the Senate subcommittee on Tuesday, said that whoever is behind the attacks on diplomats must have wanted to disrupt the normalizing of relations between Cuba and the United States.

READ MORE: Soviet Halts Microwaves Aimed at U.S. Embassy

In 2015, the United States reopened its embassy in Havana after 54 years of not having diplomatic relations.

Story continues below advertisement

That move came after Canada, which has maintained an embassy in Cuba, facilitated talks between the two countries earlier that same year.

The apparent targeting of both American and Canadian diplomatic staff has raised questions about why someone might have an axe to grind with the two countries when it comes to their presence in Cuba.

“Someone who wanted to cause friction between Cuba and the U.S. government. It makes you start to think, who would do this? Someone who doesn’t like our presence there,” Rubio told the committee.

“If it wasn’t a rogue element within the Castro government, perhaps it was a third country. Which country would want to disrupt U.S. presence in Cuba, and the logical answer is Russia.”

Rubio then raised what has become known as a Cold War medical mystery involving the aiming of low-level microwave beams by Russia at the U.S. embassy in Moscow during the 1960s.

The investigation into the effect of those beams was called Project Pandora and sent American scientists with the Defense Advanced Research Projects (DARPA) on a hunt to try and uncover whether it was possible for microwaves to cause the reports of fatigue and confusion among staff at the embassy and whether the beams could facilitate mind control.

That bombardment ended in 1979.