The destruction of the jihadists’ so-called caliphate, which was once as large as the United Kingdom and ruled over millions of people, marked a major milestone in the battle against the terrorist organization.

But American officials and Syrian fighters have warned that the group is not defeated, but has returned to its insurgent roots and continues to stage deadly attacks.

NBC had been among the dozens of news outlets reporting on the battle to push the Islamic State out of its last patch of territory, near the village of Baghouz in eastern Syria.

After the announcement of the end of the caliphate, the NBC correspondent Matt Bradley walked through the destroyed village of Baghouz, talking about how many of the Islamic State’s adherents remained committed to its ideology.

“While the caliphate may be dead, Islamic State as we know it may still be alive,” he said.

The explosion that killed the NBC team’s driver occurred after that report, but it was not immediately clear whether the group had been targeted. A United States-led coalition fighting the Islamic State has heavily bombed the area, raising concerns about unexploded ordinance that may remain.