At least 20 calves were killed when the floor of the barn they were standing on collapsed on Tuesday morning, broadcaster Omroep Gelderland reports.

In total, 94 calves fell up to two metres when the floor broke through into the pit used to collect manure. Some 70 animals, weighing upwards of 60 kilos each, were hoisted back to safety by the fire brigade and volunteers.

A spokesman for the fire service said an investigation is underway into why a supporting wall gave way, leading the floor to collapse. The shed, which is some 60 metres long, was less than one year old, a spokesman told the Telegraaf.

The farm, which has around 1,000 cows and calves, is in the village of Uddel, in Gelderland.