An investigation is being conducted into how a helicopter accidentally dropped a concrete block onto a cable car, killing nine German tourists. Answers are being sought into whether a technical fault or human error was the cause.

Six children were among the nine German skiers killed in Monday's accident in Soelden, a ski resort in the Tirol.

The block, which was to be used for construction, hit one gondola, sending it plunging down - two others swung violently, causing people to fall out.

Local media report seven people sustained severe injuries, two of which remain in critical condition.

According to Jakob Falkner, head of the Soelden cable cars, the helicopter flight above the moving cable cars had authorization.

The cable car company says the 750kg (1,650lb) block fell from a height of 300m (1,000ft).