Agriculture officials will begin culling a further 4 000 ostriches today after discovering a new pocket of avian flu among ostriches on a farm near Fort Brown.

Blood tests on the birds had confirmed the presence of the deadly virus and many of them were showing symptoms of the disease, agriculture department spokesman Segoati Mahlangu said.

The Fort Brown farm had exchanged birds with farms in the area of the original outbreak near Somerset East prior to the quarantine measures and had initially been linked to the first farms by the department´s forward and backward tracing system.

According to departmental policy, Mr Mahlangu would not name the farm on which the ostriches tested positive but it is understood to be near Fort Brown north of Grahamstown.

Residents of the area yesterday reported seeing a large pile of dead ostriches on a farm. Mr Mahlangu insisted the culling had not yet started, but he could not explain the reports.

This is the second outbreak of the disease outside of the original 30km radius control zone in the Somerset East district, since the virus was first detected in late July.

Some 2 237 ostriches on two farms in the Salem area south of Grahamstown were culled along with poultry in the area earlier this month when tests identified the virus there. These farms too had exchanged birds and workers with the Somerset East farms.

A total of 16 443 ostriches were culled on 18 farms in the Somerset East control zone. The virus was identified as the same H5N2 strain which killed chicken flocks in Asia last year.

Mr Mahlangu said it was not yet clear how many farms elsewhere had purchased ostriches from infected farms in the control zone.

"At this stage it´s just those farms (in Salem and Fort Brown). The situation is not static. We are still getting information and sero-surveillance (blood tests) is continuing."

Any ostrich farm which had "recent" dealings with those in the control zone would be investigated.

However, Mr Mahlangu insisted the disease had been contained and the Salem and Fort Brown cases were just extensions of the original outbreak.

"We have done countrywide sero- surveillance and the disease has been found only in these two areas. We have dealt with it successfully," he said. He conceded, though, that testing on flocks elsewhere in the country had not been completed yet.

Officials, meanwhile, are busy with "mopping up" operations in the Somerset East district, using a helicopter to look for stray flocks or wild ostriches which might have missed the culling net.