Members of a congressional delegation said Wednesday that two American soldiers from Alabama, who had aided Ukraine in the war against Russia, had not been heard from for several days and were missing.

Relatives of one of the 27-year-old men, along with another 39-year-old soldier, were on June 8 in the Kharkiv region of northeastern Ukraine, near the Russian border, when they heard nothing from him.

“My office is investigating with the US State Department and the Federal Bureau of Investigation (FBI) in an effort to obtain all possible information.” Robert Aderholt, a congressman in touch with the families of veterans, said.

If confirmed, they will be the first Americans to fight for occupied Ukraine since the start of the war on February 24.

The U.S. State Department says it is reviewing reports that Russian or pro-Russian separatist forces in Ukraine have captured at least two U.S. citizens.

The White House’s national security spokesman John Kirby said Wednesday that the administration could not confirm the disappearance of the two Americans. “We will do everything we can to monitor this and see what we can learn from it.”He announced.

However, he reiterated his warnings against Americans traveling to Ukraine. “Americans do not travel to Ukraine”He announced. “If you are interested in supporting Ukraine, there are many ways to do it, they are safe and effective.”