WASHINGTON — Two Navy SEAL commandos under investigation in the strangling of an Army Green Beret soldier in June in Mali have also been under scrutiny in the theft of money from a fund used to pay confidential informants, according to three service members briefed on the matter.

One Navy official said that military authorities investigated the allegations earlier this year and concluded there was insufficient evidence to take any criminal or other disciplinary action against the commandos, who are members of the elite SEAL Team 6. But another former member of the unit said the inquiry was continuing.

The revelations might shed light on a possible motive in the death of Staff Sergeant Logan J. Melgar, a 34-year-old veteran of two tours in Afghanistan, in the embassy housing he shared in the Malian capital, Bamako, with the two Navy commandos, who were on a secret counterterrorism mission in the impoverished West African nation.

Melgar’s killing marked the latest violent death under mysterious circumstances for US troops on little-known missions in that region of Africa.

Four US soldiers were killed in an ambush last month in neighboring Niger while conducting what was initially described as a reconnaissance patrol but was later changed to supporting a much more dangerous counterterrorism mission against Islamic militants in the area.

The Pentagon said last week that an inquiry into the four soldiers’ deaths would not be completed until January at the earliest.

No one has been charged in Melgar’s death, which a military medical examiner ruled “a homicide by asphyxiation,’’ or strangulation.

The initial reports to Melgar’s superiors in Germany said he had been injured while wrestling with the two Navy commandos, according to three officials who have been briefed on the investigation and who requested anonymity because of the ongoing investigation.

The Naval Criminal Investigative Service took over the case in late September from Army criminal authorities after the status of the two Navy commandos was changed from “witnesses’’ to “persons of interest,’’ meaning officials were trying to determine what the commandos knew about the death and whether they were involved.

The Navy SEALs’ potential role threatens to tarnish SEAL Team 6, the famed counterterrorism unit that carried out the raid that killed Osama bin Laden in 2011.

Until now, the biggest unanswered question in the case has been why Melgar was killed. But new clues are emerging on that front.

A US servicemember who knew Melgar said he was under the impression that the sergeant had stumbled on some sort of money-skimming scheme involving the Navy commandos.

A retired senior enlisted sailor who served in SEAL Team 6 said Melgar discovered the scam and threatened to report the Navy commandos to authorities. Melgar’s suspicions were first reported in the Daily Beast.

Both people spoke on condition of anonymity because the sergeant’s death remains under investigation. A spokesman for the Naval Criminal Investigative Service, Ed Buice, declined to comment on the homicide investigation.

Special Operations troops from a range of units can earn qualifications that let them recruit sources for intelligence and pay them. These individuals might handle payments from small cash bags up to storage lockers filled with currency.