KNOXVILLE, Tenn. (WATE) — Passengers aboard the Dollywood Express were forced to evacuate due to a mechanical issue on Sunday.

Officials say the incident happened just before 8:30 p.m. on Sunday at Dollywood, the Dolly Parton-owned theme park in Pigeon Forge, Tennessee. All passengers on board were unloaded safely and no injuries were reported.

The cause of the mechanical issue has not been released yet.

The Dollywood Express features a 20-minute train ride, led by a 110-ton coal-fired steam engine. It follows a five-mile trek through the foothills of the Great Smoky Mountains.

Two steam engines operate on the Dollywood Express, Engine 192, or “Klondike Katie,” and Engine 70, known as “Cinderella.”

The engines were originally part of Rebel Railroad, a park built in 1961 that once stood where present-day Dollywood now sits. Both Klondike Katie and Cinderella joined the park after serving in Alaska in World War II.

Klondike Kaite and Cinderella were built by the Baldwin Locomotive Works in Philadelphia in 1943 and 1938, respectively. The trains were bought from the Army by the original owners of the Rebel Railroad.

“Klondike Katie originally was built for speed, while Cinderella had more power and torque to pull heavier loads,” according to Dollywood. It’s not clear which of the engines was operating the Dollywood Express when the incident happened.