(CNN) - The twelve member Green Beret-led team that was ambushed by militants in Niger earlier this month became separated during the firefight and attempted to mount a counterattack, US officials told CNN Friday.
The two groups also lost contact with one another during the battle, likely adding to the confusion surrounding the engagement, one of the officials said.
The squad was traveling with 30 Nigerien soldiers when they were attacked by approximately 50 ISIS-affiliated fighters armed with rocket-propelled grenades, mortars, and heavy machine guns, according to US military officials.
In the subsequent gun battle, which lasted for hours, four US soldiers were killed and two were wounded. Their Nigerien interpreter and four Nigerien soldiers were also killed. US-Nigerien forces managed to kill 20 militants during the fight on October 4 using primarily small arms.
At least one vehicle, an unarmored pick-up truck, was disabled by enemy fire in the initial ambush.
During the firefight, the US team separated into two groups, with some of the US soldiers dismounting from their vehicle to maneuver on foot in an attempt to counterattack and out-flank their attackers, multiple sources briefed on the investigation told CNN.
A Nigerien soldier who was part of the unit that later came to the aid of the joint US-Nigerien force told CNN that wounded Nigerien troops told him that the first two vehicles had been hit by militants and subsequently split from the convoy.
As the battle continued, one group of American soldiers lost communication with a second group that included at least some of the Americans killed in action, one source familiar with investigative reports said.
Yet despite the two groups possibly losing contact with one another, the Pentagon said Thursday that that at least some of the team maintained the ability to radio back to their base, which enabled them to call in for air support about one hour after the ambush began.
"Anytime you put a unit out there in place like this, you've got good communications and procedures, you've got a solid, thorough, comm plan that's been tested with backups," Joint Staff Director Lt. Gen. Kenneth McKenzie said in a briefing with reporters at the Pentagon Thursday.
"Somebody's always going to answer the radio on the other end when the commander on the ground presses it," McKenzie added.
An unarmed surveillance drone arrived within minutes after receiving the call for support, and armed French Mirage jets flew overhead an hour later, with officials saying the French jets' show of force helped disperse the remaining attackers.
CNN has also learned that the White House was initially told that all four soldiers could be missing in the wake of the deadly attack.
According to an administration official, initial information conveyed to the White House stated that a total of four soldiers were missing in action; the military soon updated its reporting, changing the status of the four soldiers to three killed in action and one missing, Sgt. La David Johnson.
A large-scale search and rescue operation involving US, French and Nigerien troops was launched soon after US officials realized US service members were unaccounted for.
Elite US special operations forces troops were flown in from the continental US to aid in the recovery effort.
US Navy SEALs were deployed to a US military base in Sigonella, Sicily, in anticipation of a possible rescue attempt.
Johnson would not be recovered for another 48 hours.
French Super Puma military helicopters and contractor aircraft landed to evacuate the wounded US and Nigerien troops, and then later returned for the bodies of the dead.
The bodies of three of the fallen soldiers -- excluding Johnson -- were recovered by a separate team of Niger-based US military personnel using contractor aircraft, according to two US defense officials.
Johnson's body was finally recovered 48 hours after the attack, nearly a mile away from the scene, four administration officials familiar with the early assessment of what happened told CNN last week.
Defense officials have stressed that at no point were any of four dead soldiers "abandoned," saying that the Nigerien relief force accompanied by "a handful" of French military advisers stayed on scene until the bodies were airlifted out.
A US intelligence official told CNN this week that ISIS in the Greater Sahara is likely responsible for the ambush.
ISIS in the Greater Sahara has attacked pro-Bamako militias supporting French and United Nations forces deployed in northern Mali, and regional security forces in Burkina Faso and Niger. ISIS in the Greater Sahara was established in 2015 after the group's current leader, Adnan Abu Walid al-Sahrawi, broke from the al Qaeda associated al-Murabitun group.