U.S. and Syrian forces decided not to strike a convoy carrying as many as 200 Islamic State in Iraq and Syria (ISIS) fighters fleeing the northern Syrian city of Manbij out of concern for civilian casualties, a spokesman said Tuesday.

A “significant number" of vehicles carrying ISIS fighters fled north after U.S.-backed Syrian forces retook the strategic city from the terrorist group last weekend.

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“We did not conduct any strikes because [every vehicle] had civilians in it or on it, and so we watched, we kept track,” said Army Col. Chris Garver, spokesman for the coalition. “They went north.”

Garver said the fighters are still being tracked. He would not specify their locations as part of an "ongoing operation."

Garver also would not say whether the fighters have tried to flee across the porous northern border into Turkey, where ISIS foreign fighters have crossed to join the fight in Syria.

The civilians, likely a mixture of family members and captives, have not gone back to Manbij, Garver said.

“There were some that were being held unwillingly and some that were traveling willingly with them. We don’t know that, which is why we had to treat them all as noncombatants,” he said.

Garver said the Syrian commander on the ground and the U.S. commander in charge of the air war made the decision not to target the convoy.

The U.S. has come under scrutiny by human rights groups and activists for potentially killing civilians in the Al Tokhar village during the Manbij offensive, which the U.S. has provided air support for.

Garver said ISIS may have learned from its hasty departure from Fallujah, Iraq, where ISIS fighters fled in hundreds of vehicles that were then targeted by the U.S.-led coalition and Iraqi air forces.

"It looks like they certainly paid attention and now we'll adapt and change as well," he said.