A senior commander at the US naval base at Guantanamo Bay has been charged with obstruction of justice after an inquiry into the death of a civilian.
Safety manager Christopher Tur drowned in 2015 close to the base in Cuba.
Navy Capt John Nettleton is accused of concealing evidence, making false statements and falsifying records in the aftermath.
Officials believe he had an affair with Tur’s wife, and fought with him shortly before he went missing.
A 36-page federal indictment alleges Mr Nettleton lied to investigators and had a violent confrontation with Tur over the alleged affair.
Tur’s body was discovered floating in waters nearby on 11 January 2015.
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An autopsy revealed Tur died from drowning, but he had also sustained broken ribs and a cut to his head.
Officials believe Capt Nettleton and Tur’s wife agreed not to tell investigators about their extramarital affair.
However, an anonymous complaint reportedly reached naval investigators in the aftermath of Tur’s death.
Capt Nettleton was then relieved of his duty and reassigned to Florida.
Guantanamo Bay, in south-eastern Cuba, has been leased by the US since 1903. In 2001, then-President George W Bush opened a detention centre at the base to accommodate foreign terror suspects after the 9/11 attacks.
‘A reminder’ about Guantanamo
Analysis by Tara McKelvey, BBC News, Washington
As a base commander, Capt Nettleton was not responsible for the detention facilities on the island – that’s handled by a rear admiral. Yet his case shines a spotlight on operations at Guantanamo Bay and acts as a reminder that the prison is still open, 17 years after the first detainees arrived.
Jana Lipman, the author of a book about the island, describes it as “a mostly Constitution-free zone”, and 40 men are still being held there.
During the presidential campaign, Trump promised to “load it up with some bad dudes”, and as president he signed an executive order to keep the prison running.
His enthusiasm for the place has made one thing clear: the chapter on Guantanamo, a controversial part of US history, remains open – with no real ending in sight.
A Naval Criminal Investigative Service (NCIS) refused to comment on the case on Wednesday.
“NCIS does not comment on open investigations,” spokesman Jeff Houston said.
Tur’s older brother welcomed news about the charges, the Associated Press news agency reports.
“It’s not a homicide charge, but he’s facing some serious jail time,” Michael Tur said.
A lawyer for Capt Nettleton said his client was “innocent of all charges” and said he “looks forward to the opportunity to tell his side of the story”.
After the indictment was unsealed, the 53-year-old reportedly handed himself into NCIS who transferred him to federal court.
He has plead not guilty and been released on bail, US media report.