Story highlights During the firefight, the US team separated into two groups in an attempt to counterattack

As the battle continued, one group of American soldiers lost communication with a second group that included the four Americans killed

(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.

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