Experts have returned to a south Wales beef farm to trace the source of anthrax which has killed two cows.
Seven cows died of anthrax on the farm 35 years ago
The alert at the farm, named on Monday as Ynys Gau, near Gwaelod-y-Garth, outside Cardiff, was sparked after the sudden deaths of six cows in the herd.
Wales' chief vet has given reassurances that the anthrax outbreak does not present a risk to the public.
The last British case of the disease was in north Wales, in a cow on a Wrexham farm in 2002.
The anthrax was discovered at Ynys Gau farm - said to have a herd of about 35 suckler cows - through routine testing. Farmers are required to report the sudden and unexpected death of livestock.
The other four carcasses were incinerated elsewhere and the workers there advised of health and safety procedures.
The assembly government has confirmed the farm had tested positive for anthrax 35 years ago.
Chief veterinary officer for Wales Dr Christianne Glossop said the farm had been isolated and presented no risk to the public.
She said the farm had not put an animal in the food chain for almost a year.
Testing of the farmland to identify the most likely source of the infection was likely to take days rather than weeks, she said, adding the outbreak 35 years ago was the most likely cause.
Speaking on BBC Radio Wales on Monday, Dr Glossop said there was no need to test other animals on the farm - apart from the rest of the herd - or herds on neighbouring farms.
"The public should not be concerned. They can't go on the farm, there's absolutely no reason why anything is going to spread from the farm - that's not how anthrax works," she said.
"We know that the spores can live in the ground for long periods of time, so it is possible this outbreak is linked to the seven cattle that died [on this farm] 35 years ago, but that in itself shows you that the spores can lie dormant and not cause problems for long periods of time."
Footpaths crossing the farm have been closed
A cow was "more likely to die from being struck by a bolt of lightning" than from anthrax.
No animals or people are allowed on or off the farm without a licence and footpaths across the land have been closed.
Restrictions will remain in place until experts are satisfied the disease is "completely contained".
Anthrax spores can persist in the environment, notably soil, for years. An anthrax infection can be treated successfully with antibiotics when the disease is identified early.
Environment Agency and State Veterinary Service officials will be at the farm on Monday.
Alan Gardner, vice-president of the Farmers Union of Wales, said the industry was "very concerned" at the outbreak, but said he had been reassured by the "speedy action" of the authorities.
Anthrax is a highly infectious and contagious disease but uncommon in humans
Under certain conditions it forms spores that may persist for many years in the environment
Cutaneous anthrax is the most common type, accounting for 95% of cases
Before 2002, the last confirmed case of anthrax in cattle occurred in Lanarkshire in 1997
Local veterinary inspectors are involved in monitoring and all unexplained sudden deaths in livestock are reported
He said: "Outbreaks of anthrax are very, very rare these days, the last outbreak being in 2002. Having said that, outbreaks occurred fairly regularly - even on an annual basis - up until as recently as 1997.
"The measures to deal with outbreaks of anthrax are very effective and I'm sure the industry feel quite confident this outbreak will be controlled fairly quickly."
Mr Gardner said that even though the word anthrax could be alarming, the chances of humans being infected were small.
"For it to be infectious to humans they have to ingest over two-and-a-half thousand spores per hour, so it really doesn't pose any risk to humans unless they get very close to it," he said.