A second official on the National Security Council was reportedly struck with the mysterious condition known as Havana Syndrome last year while near the entrance to the White House grounds, CNN reports.

Sources close to the matter told CNN that the official experienced more severe symptoms than the previous case that had been reported in April.

The case occurred last year, CNN reports, several weeks after the presidential election. 

The mysterious Havana Syndrome got its name after a number of diplomats from the United States and Canada who were stationed in Havana, Cuba, reported signs of vertigo, headaches and insomnia. The cause of the illness, which was first observed in 2016, has yet to be identified. However, it has afflicted more than 130 U.S. diplomats, spies and troops.

CNN had previously reported two separate incidents of Havana Syndrome, one that occurred near the White House and another in a Virginia suburb in 2019. Both cases happened to White House officials.

“The health and well-being of American public servants is a paramount priority for the Biden administration," a White House official told The Hill last month when news of the first case broke. "We take all reports of health incidents by our personnel extremely seriously. The White House is working closely with departments and agencies to address unexplained health incidents and ensure the safety and security of Americans serving around the world."

Senate Intelligence Committee leaders in April vowed to “get to the bottom” of the strange illness after the case near the White House was reported.

“For nearly five years, we have been aware of reports of mysterious attacks on United States Government personnel in Havana, Cuba and around the world," Sens. Mark Warner (D-Va.) and Marco Rubio (R-Fla.) said in a joint statement last month. "This pattern of attacking our fellow citizens serving our government appears to be increasing. The Senate Intelligence Committee intends to get to the bottom of this."