The AFCD was informed by the person-in-charge of the farm about the chicken deaths on 9 August.

Samples were collected and chicken carcasses were taken from the farm on the day and on August 11 for Polymerase Chain Reaction tests (PCR) and virus isolation, bacterial culture and histopathology.

All the samples yielded negative test results for avian influenza and Newcastle disease.

The AFCD officers found the health of the chickens improving and the deaths have gradually subsided.

The cumulative total of chicken deaths amounted to about 4,300.

An AFCD spokesman said: "Based on the test results, the clinical history and the findings of the investigation, the deaths were likely caused by heat stress as a result of the ventilation system failure in the shed consequent to a power outage.

"The AFCD will continue to monitor the situation. We will consider lifting the sales suspension when the survival rate of the poultry on the farm returns to normal."

Advice on improvement measures has been provided to the farmer, including the installation of power backup facilities, monitoring regularly the operation of the facilities at the farm and implementing proper bio-security measures. He has also been reminded to report any irregularities to the AFCD promptly.

Inspection of all local chicken farms has been completed and no irregularities have been observed.

The AFCD will continue to implement the prevention and control measures against avian influenza and maintain close liaison with chicken farmers to ensure the health of the chickens and that those put on the market have passed the avian influenza virus test.