FOUR hundred sheep were killed in a truck accident in southern NSW yesterday.

A semi-trailer overturned on a wet road near Corowa - killing the sheep and injuring the driver and his young son.

The two-tier stock transport truck was travelling on the Mulwala-Barooga Road, after leaving the Corowa stockyards, when it left the road about 6.40pm yesterday.

``The vehicle veered onto the gravel verge in heavy rain and the driver lost control,'' a NSW Police spokesman said .

``The rig came to rest across the east-bound lanes of the roadway.''

Police say about 300 sheep were killed in the crash, and another  100 animals had to be put down because of their injuries. Just 50 sheep survived.

The truck's 40-year-old driver, from Altona in Melbourne, also suffered facial injuries while his 10-year-old son was treated for suspected spinal and chest injuries.

Both were taken by ambulance to Yarrawonga Hospital, in Victoria.

Albury Police are investigating the cause of the crash.