"Though other sources of neurotoxins are possible, our insecticidal hypothesis gains contextual support given Cuba’s well-documented efforts to aggressively mitigate the spread of the Zika virus by means of mass indoor and outdoor fumigations in 2016 and thereafter", the report published by the Canadian Foreign Ministry said.
The Canadian study found evidence consistent with "overexposure to cholinesterase inhibitors as the cause of brain injury," the report added.
The ministry also confirmed the presence of cholinesterase-inhibiting insecticides including Temephos, an organophosphorus poison used in Cuba to kill mosquito larvae.
The same chemicals are used in nerve gases such as Sarin and VX, and also in at lower concentrations in some insecticides, according to the report.
In August 2017, the US State Department said nearly two dozen diplomats working at the US embassy in Cuba were affected in an incident involving a mysterious audio device and some of the diplomats suffered permanent hearing loss and possible brain injuries. Washington accused Cuba of carrying out the "attacks."
Previous speculation has focused on weaponized microwave devices, in part due to US diplomats reporting loud noises prior to reporting symptoms. The Canadian diplomats with similar symptoms reported, however, no unusual sounds, the report said.
The State Department had even established a task force to respond to the mysterious incidents, because US diplomats in China have also complained of symptoms similar to the ones suffered by their colleagues in Cuba.
Havana has, however, denied any Cuban involvement in the incidents.