Scientists investigating an outbreak of bird flu at a farm near Banbury suspect mallard ducks reared for sport shooting may have been responsible.

An official report on the June 4 outbreak said the most likely explanation was infection from a ducks on a pond about 100 metres from the first affected building.

The Department for Environment, Food and Rural Affairs said "a number" of theories about the outbreak at the 150-acre farm were under consideration but the most likely explanation was infection from separate premises or from wildlife.

It said the building in which the disease was believed to have first entered was situated about 100m from a small pond populated by "a small flock of mallard ducks that were reared for sport shooting".