Human error is blamed for the Taiwan train wreck that killed 17 people and injured 102 on the weekend.

The train's conductor Tsai Chen-sen was released on bail Sunday. Officials say he could face charges of manslaughter and endangering public security.

"Human errors are to blame" for the accident, chief prosecutor Lo Chien-hsun told reporters after he and a team of experts from the state-run Taiwan Railway Administration combed the crash site.

Lo said the coupling that links the brakes of the four-carriage train to the locomotive was switched off, resulting in brake failure in the carriages but not in the locomotive.

"That was why the accident happened. The brake system of the carriages simply did not work while the train was running along a downslope on the biggest curve of the mountain railway," Lo said.

"Apparently the driver, the assistant and the train's captain did not check before operating the train yesterday." The train was loaded with families on weekend outings to Alishan mountain, a popular destination for tourists in Central Taiwan's Chiayi area.

The derailment occurred as the four-carriage train carrying 200 passengers and three staff was crossed a 20-meter-long bridge, according to the Taiwan Forestry Bureau.

The first carriage had just passed over the bridge when it hit the edge of the mountain. The derailment left the middle carriages suspended over the bridge.

The fourth carriage snapped off the train, pitching it into a five-meter ravine. The locomotive, traveling at the end of the train, escaped unscathed.

Chen-sen's assistant Liu Po-yueh was released early Sunday after questioning by prosecutors and police.

Prosecutors were also investigating how a helicopter airlifting victims from the crash site also crash-landed. There were no serious injuries.

Grief-stricken relatives returned to the crash site Sunday to burn "ghost money" as Taoist monks chanted Buddhist prayers to pacify the spirits of the dead according to Taiwanese tradition.