WASHINGTON — The strange sound came at night: a crack like a marble striking the floor of the apartment above them.
Mark Lenzi and his wife had lightheadedness, sleep issues and headaches, and their children were waking up with bloody noses — symptoms they thought might be from the smog in Guangzhou, China, where Mr. Lenzi worked for the State Department. But air pollution could not explain his sudden memory loss, including forgetting names of work tools.
What began as strange sounds and symptoms among more than a dozen American officials and their family members in China in 2018 has turned into a diplomatic mystery spanning multiple countries and involving speculation about secret high-tech weapons and foreign attacks.
One of the biggest questions centers on whether Trump administration officials believe that Mr. Lenzi and other diplomats in China experienced the same mysterious affliction as dozens of diplomats and spies at the American Embassy in Cuba in 2016 and 2017, which came to be known as Havana Syndrome. American employees in the two countries reported hearing strange sounds, followed by headaches, dizziness, blurred vision and memory loss.
But the government’s treatment of the episodes has been radically different. The State Department, which oversaw the cases, has produced inconsistent assessments of patients and events, ignored outside medical diagnoses and withheld basic information from Congress, a New York Times investigation found.
In Cuba, the Trump administration withdrew most of its staff members from the embassy and issued a travel warning, saying U.S. diplomats had experienced “targeted attacks.” President Trump expelled 15 Cuban diplomats from Washington and started an independent review, though Cuba denied any involvement.
The administration took a softer approach with China. In May 2018, Secretary of State Mike Pompeo, who was the C.I.A. director during the Cuba events, told lawmakers that the medical details of one American official who had fallen ill in China were “very similar and entirely consistent” with the syndrome in Cuba. The administration evacuated more than a dozen federal employees and some of their family members.
The State Department soon retreated, labeling what happened in China as “health incidents.” While the officers in Cuba were placed on administrative leave for rehabilitation, those in China initially had to use sick days and unpaid leave, some officers and their lawyers say. And the State Department did not open an investigation into what happened in China.
The administration has said little about the events in China and played down the idea that a hostile power could be responsible. But similar episodes have been reported by senior C.I.A. officers who visited the agency’s stations overseas, according to three current and former officials and others familiar with the events.
That includes Moscow, where Marc Polymeropoulos, a C.I.A. officer who helped run clandestine operations in Russia and Europe, experienced what he believes was an attack in December 2017. Mr. Polymeropoulos, who was 48 at the time, suffered severe vertigo in his hotel room in Moscow and later developed…