A Taiwanese train has derailed, killing 17 people and injuring more than 150 others in the central county of Chiayi.

The four-car train was carrying some 170 passengers down Mount Ali from a popular mountain resort when it derailed Saturday.

The cause of the derailment is not yet known, but rail authorities say a preliminary investigation points to faulty brakes.

Surviving passengers say the train raced down the hill like a roller coaster.

The Council of Agriculture says the cars tumbled into a ravine after crossing a bridge. Observers say two of the cars hung off the bridge in mid-air.

Rescue efforts were complicated when a helicopter crashed. Officials say the ten victims on board the helicopter were not injured further.

The Alishan forest railway is one of the three remaining mountain-climbing railway systems in the world. It was built to haul cypress logs down the mountain when Taiwan was under Japanese colonial rule before World War Two. Now it mostly carries tourists.