Military personnel associated with the United States Department of Defense have been directed to disclose any symptoms of the Havana Syndrome, according to media reports citing an internal memo. The directive also includes contractors and civilian officials.

The memo, which was sent to nearly 2.9 million officials, defines suspected signs of an attack, which include excessive pressure, heat and noise, according to reports from New York Times.

Secretary of Defense Lloyd Austin wrote in the memo, "Timely reporting is essential and starts with knowing what to do if you experience A.H.I", New York Times reported. AHI stands for anomalous health incident.

The request made by the Department of Defense seems to be the most recent effort for building intelligence around the mystery syndrome. Intelligence officials have so far struggled to assign any blame for the unexplained situation.

Deputy Director of the Central Intelligence Agency said in a statement, "There is a classic intelligence problem, and we are approaching it with the same techniques. This is a serious issue. It is real, it is affecting our officers, it is affecting others around their community and in government", according to reports from New York Times.

Earlier this week, Cuba issued its most detailed report to date from prominent local scientists criticizing allegations that United States and Canadian diplomats were subject to mystery illness while posted on the island and developed health issues.

More than two dozen United States and a dozen Canadian embassy workers in Cuba's Havana reported falling ill in 2016 and 2017, leading United States officials at one point to assert they had been victims of "sonic attacks".

The alleged attacks strained the relations of Cuba with both the United States and Canada. While Canada significantly pulled back its diplomatic presence, Americans shut down most operations in the country, according to reports from Associated Press.