Two highly pathogenic cases of bird flu were confirmed in England on Saturday, just over a week since the government ended the mandatory hosing order.
The disease was confirmed in captive birds at a premises near Ringstead, Northamptonshire, while another outbreak occurred on a commercial poultry farm in Doncaster, South Yorkshire.
The government said a 3km controlled zone had been declared around both impacted sites, and a bird cull would be enacted.
The fresh outbreaks follow the lifting of the mandatory housing order , on Tuesday 18 April.
The strict measure was introduced in November 2022 as one of a range of measures to stop the spread of avian influenza.
The scale of outbreaks across the UK and Europe have been unprecedented, with over 330 cases confirmed across the country since late October 2021.
Poultry farms have been hit particularly hard, with approximately four million farm birds culled.
Dr Christine Middlemiss, the UK’s chief veterinary officer, said 'scrupulous biosecurity' remained the most critical form of defence to help keep birds safe.
She said: “It is thanks to the hard work of all bird keepers and vets who have played their part in keeping flocks safe this winter that we are in a position to take this action.
"However, the unprecedented nature of this outbreak has proven it’s more important than ever for bird keepers to remain vigilant for signs of disease and maintain stringent standards of biosecurity.”
Chief Veterinary Officer for Wales, Richard Irvine added: "Whether keepers have a few birds or a thousand, it is vital the very highest standards of biosecurity are maintained.
“Vigilance is also key, and it’s important any signs or suspicion of avian influenza is reported immediately."