Smoke in the control tower at Newark Airport forced an evacuation this morning, prompting a temporary ground stop and a shift of air traffic controllers to an alternate tower location.

Fire crews began investigating the smoke around 7:30 a.m. Officials later said grinding gears in an elevator caused the condition.

Controllers were moved from the main tower to the airport’s TC ramp tower, where operations were expected to resume within minutes.

Operations were expected to resume once controllers were fully established in the temporary ramp tower.

No injuries or structural damage were reported, according to the FAA.

The ground stop was lifted around 8:30 a.m.