The U.S. State Department said on Thursday that the number of U.S. diplomats affected by the alleged "acoustic attacks" has jumped to 26.
One new case was confirmed following a medical evaluation since last week, said the State Department Spokesperson Heather Nauert in a statement.
The State Department reported the 25th case last Thursday as one U.S. diplomat working at the U.S. Embassy in Havana was medically confirmed to have experienced health effects on June 21. It was also the first medically confirmed case in Havana since August, 2017.
The two new cases resulted from a single occurrence in late May in a diplomatic residence in which both officers were present, Nauert added.
The spokesperson said Washington has informed Havana about the latest case and the Cuban government said it will continue its investigation.
Over 20 U.S. diplomats suffered from what Washington called "acoustic attacks" between November 2016 and August 2017. The incidents led to the partial closure of the U.S. embassy in Havana, expulsion of 15 Cuban diplomats who worked at the embassy in Washington, and a halt in issuing U.S. visas in Havana.
Cuba rejected the accusation, initiated an investigation, and urged the United States to present evidence of the alleged attacks.