Fifteen Cuban diplomats must leave the United States within seven days over the ongoing and mysterious attacks against American personnel in Havana, the State Department announced Tuesday.

"The decision was made due to Cuba's failure to take appropriate steps to protect our diplomats in accordance with its obligations under the Vienna Convention," Secretary of State Rex Tillerson said in a Tuesday morning statement.

A senior U.S. diplomat informed the Cuban government of the expulsions Tuesday morning, which come just days after the Trump administration withdrew most U.S. government personnel from Cuba. The decision coincided with the announcement that the number of Americans harmed by the attacks, which have caused hearing loss and other "cognitive issues" over the last year, has risen to 22.

"This move does not signal a change of policy or a determination of responsibility for the attacks on U.S. government personnel in Cuba," a State Department official told reporters Tuesday morning. "We are maintaining diplomatic relations with Havana. The decision on expulsions was taken due to Cuba's inability to protect our diplomats in Havana, as well as to ensure equity in the impact on our respective operations."

The State Department slashed U.S. staff in Havana to emergency levels Friday and warned Americans against traveling in the country. Officials have been unable to determine "who or what" has caused the attacks, some of which took place in hotels that tourists frequent.

"We have no way of advising American citizens on how they could mitigate such attacks, [and so] we felt that we must warn them not to travel to Cuba," the State Department official said Friday.

Raul Castro's regime, which has offered to help investigate the attacks and denied any culpability for the attacks, criticized the withdrawal of American personnel.

"We consider that the decision announced by the Department of State is hasty and that it will affect the bilateral relations, specifically, the cooperation in matters of mutual interest and the exchanges on different fields between both countries," Josefina Vidal Ferreiro, the top Cuban diplomat for U.S. affairs said Friday.

The attacks have unfolded since November of last year, when officials in Havana began to report symptoms such as headaches. That list expanded to include "dizziness, tinnitus, balance problems, visual complaints, headache, fatigue, cognitive issues, and difficulty sleeping."

The most recent documented attack took place in August, an incident that brought the known total of people affected to 21. But the State Department determined Monday that another American who has been suffering various symptoms since January was also a victim of the attacks.

That diagnosis was not the direct cause of the decision to expel the Cuban officials, however. "This information was confirmed yesterday after the decision making process for the expulsion was well underway," the State Department official said Tuesday.

The State Department was under congressional pressure to punish Cuba more directly even before the latest diagnosis was confirmed. "[I]t is weak, unacceptable and outrageous for the U.S. State Department to allow Raul Castro to keep as many of his operatives in the U.S. as he wants," Sen. Marco Rubio, R-Fla., said Friday.

The State Department's latest decision takes a step toward Rubio's preferred rebuke, but they targeted fewer officials and stopped short of declaring them persona non grata, the most extreme form of diplomatic censure for individual officials.

"The Cuban government has told us it will continue its investigation into these attacks and we will continue to cooperate with them in this effort," the State Department official said. "We will also continue our own investigation into these attacks."