The US on Thursday said it was aware of reports that a third American citizen has gone missing after travelling to Ukraine, after two former soldiers from Alabama were reported missing earlier this week.
“There are reports of one additional American whose whereabouts are unknown … Our understanding was that this individual had travelled to Ukraine to take up arms,” State Department spokesman Ned Price said.
Officials confirmed that they have not yet asked Moscow about the other two Americans reportedly captured after going to the country to fight against Russian forces.
Relatives of veterans Andy Tai Ngoc Huynh and Alexander Drueke, both from Alabama, have been in contact with both Senate and House offices seeking information about the men's whereabouts, press aides said.
Robert Aderholt, a congressman from Alabama, said Mr Huynh had volunteered to fight with the Ukrainian military against Russia, but relatives have not heard from him since June 8, when he was in the Kharkiv region of north-eastern Ukraine, near the Russian border.
Mr Huynh and Mr Drueke were travelling together, an aide to Mr Aderholt said.
“As you can imagine, his loved ones are very concerned about him,” Mr Aderholt said in a statement. “My office has placed inquires with both the United States Department of State and the Federal Bureau of Investigation trying to get any information possible.”
Terri Sewell, another Alabama representative, said Mr Drueke's mother had reached out to her office earlier this week after she lost contact with her son.
The US State Department said it was looking into reports that Russian or Russian-backed separatist forces in Ukraine had captured at least two American citizens. If confirmed, they would be the first Americans fighting for Ukraine known to have been captured since the war began on February 24.
“We are closely monitoring the situation and are in contact with Ukrainian authorities,” the department said in a statement emailed to reporters. It declined further comment, citing privacy considerations.
John Kirby, a national security spokesman at the White House, said on Wednesday that the administration was not able to confirm the reports about missing Americans.
“We’ll do the best we can to monitor this and see what we can learn about it,” he said.
However, he reiterated his warnings against Americans going to Ukraine.
“Ukraine is not the place for Americans to be travelling,” he said. “If you feel passionate about supporting Ukraine, there’s any number of ways to do that that are safer and just as effective.”
A court in Donetsk, under separatist control, sentenced two Britons and a Moroccan man to death last week.
Mr Huynh's fiancee, Joy Black, posted publicly on Facebook that his family was in contact with the Drueke family and government officials and that nothing had been confirmed other than that the two were missing.
“Please keep Andy and Alex and all of their loved ones in prayer. We just want them to come home,” she wrote.
Adam Kinzinger, a representative from Illinois, tweeted that the Americans “have enlisted in the Ukrainian army, and thus are afforded legal combatant protections”.
“As such, we expect members of the Legion to be treated in accordance with the Geneva Conventions,” he said.
It was unclear whether Mr Kinzinger had any further information about the men.
He was commenting on a tweet sent earlier on Wednesday by Task Force Baguette, a group of former US and French servicemen, saying that two Americans fighting with them had been captured a week ago. The group said Ukrainian intelligence had confirmed the information.
Early in the war, Ukraine created the International Legion for foreign citizens who wanted to help defend against the Russian invasion.
Mr Huynh spoke to his local newspaper, The Decatur Daily, shortly before flying to Eastern Europe in April.
He explained that he was studying robotics at Calhoun Community College but couldn’t stop thinking about Russia’s invasion.
“I know it wasn’t my problem, but there was that gut feeling that I felt I had to do something,” Mr Huynh told the newspaper.
“Two weeks after the war began, it kept eating me up inside and it just felt wrong. I was losing sleep. … All I could think about was the situation in Ukraine.”
He said he decided to fly out once he learnt that young Ukrainians were being drafted into service.
The newspaper reported that Mr Huynh enlisted in the Marines when he was 19 and served for four years, though he did not see combat.
Agencies contributed to this report