Mysterious health incidents at the U.S. Embassy in Havana happened as recently as August, the State Department said Friday, despite earlier assessments that the attacks had stopped.

The U.S. has also updated its tally of individuals affected by the incidents from 16 to 19, according to The Associated Press.

“We can confirm another incident which occurred last month and is now part of the investigation,” State Department spokeswoman Heather Nauert said.

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The incidents began last fall when U.S. diplomats at the embassy began reporting unexplained hearing loss. The U.S. has launched an investigation into the matter.

U.S. officials previously said that the attacks continued until spring 2017, but has now reported the most recent incident occurring months later in August.

“We can’t rule out new cases as medical professionals continue to evaluate members of the embassy community,” Nauert said, according to the AP.

U.S. officials initially blamed the mysterious health symptoms on a covert sonic device, though they have not uncovered or identified any such device.

In response to the attacks, the U.S. expelled two Cuban diplomats from the country's embassy in Washington in May.

The Cuban government has vehemently denied any involvement in the incidents, and is conducting its own investigation into the matter.