A handful of U.S. tourists who recently returned from Cuba have complained about symptoms similar to those experienced in mysterious sonic attacks against U.S. government workers.

The State Department said Friday that several Americans who don't work for the government have reported similar symptoms after traveling to the country. But the U.S. government "cannot verify the claims" or any potential connection to the attacks said the official, who wasn't authorized to comment by name and spoke on condition of anonymity.

"Since we issued the September 29 Travel Warning, we have received a handful of reports from U.S. citizens who report they experienced similar symptoms following stays in Cuba," a State Department official told CBS News. "We have no way of verifying whether they were harmed by the same attacks targeting official U.S. employees."

At least 22 U.S. Embassy employees on the communist-run island have reported injuries from attacks "of an unknown nature," according to the State Department. Symptoms have included ear issues, hearing loss, dizziness, headache, fatigue, cognitive issues and difficulty sleeping.

The State Department said last week that investigators have been unable to determine who is responsible or what is causing these attacks.

The Associated Press, citing unnamed U.S. officials, reported that American intelligence operatives in Cuba were among the first and most severely affected victims.

In some of the cases, U.S. operatives have suffered brain injury and hearing loss that has not healed. The American spies affected also reported hearing an unsettling sound inside and sometimes outside their Havana homes, described as similar to loud crickets. Then they fell ill with a range of physical symptoms.

In a security notice Friday to American citizens, the State Department said Americans who believe they may have symptoms after visiting Cuba should "consult a medical professional."

The United States last week issued a travel warning that urges American travelers to stay away from Cuba. The warning said attacks on government personnel have occurred in Havana hotels and the U.S. can't make sure that Americans who stay at hotels wouldn't be harmed. It also included the most detailed list to date of symptoms the victims have experienced, including hearing, cognitive and sleeping problems.

The Associated Press contributed to this article.