This article is more than 2 years old

This article is more than 2 years old

Russia is the main suspect in US agencies’ investigation of mysterious illnesses in American personnel in Cuba and China, NBC News reported on Tuesday.

Evidence from communications intercepts has pointed to Moscow’s involvement during the investigation involving the FBI, CIA and other agencies, three unidentified US officials and two other people briefed on the investigation told NBC.

The evidence, however, is not conclusive enough for the United States to assign blame publicly to Moscow, according to the NBC report.

FBI and CIA officials did not immediately return a request for comment on the report.

US officials said in July that they were still investigating health problems at the US embassy in Cuba, and do not know who or what was behind the mysterious illnesses, which began in 2016 and have affected 26 Americans.

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The US withdrew more than half of its Havana diplomats last year and expelled 15 Cubans after 24 embassy staff and family reported a bizarre list of symptoms, ranging from headaches, dizziness and difficulties in sleeping, to problems with concentration, balance, vision and hearing.

The state department said in June it had also brought a group of diplomats home from Guangzhou, China, over concern they were suffering from a mysterious malady resembling brain injury.

Cuban 'acoustic attack' report on US diplomats flawed, say neurologists Read more

However, neurologists and other brain specialists have disputed a medical report commissioned by the US government, which found that staff at the US embassy in Havana suffered concussion-like brain damage.

Cuban officials, who are conducting their own investigation, have denied any involvement or knowledge of what was behind it.

The United States believes sophisticated electromagnetic weapons may have been used on government workers, possibly in conjunction with other technologies, NBC reported.

Physicists have voiced doubts that such weapons were even feasible, but the US military has been trying to reverse-engineer the weapon or weapons used to harm the diplomats, including by testing various devices on animals, NBC said, citing Trump administration officials, congressional aides and others.

Part of the work is being done at the directed energy research program at Kirtland air force base in New Mexico, where the military has giant lasers and laboratories to test high-power electromagnetic weapons, including microwaves, NBC said.

• Reuters contributed to this report