The Bernard Matthews plant at the centre of a bird flu outbreak will not face prosecution, the Food Standards Agency has said.
The outbreak took place in February
An investigation concluded there was no evidence that food waste at the plant may have been stored inappropriately.
Avian flu was found at the site in Holton, Suffolk, on 3 February and 2,600 turkeys died of it - a further 159,000 birds were culled.
Bernard Matthews said it has "systems in place" to meet hygiene requirements.
Last month restrictions on the movement of poultry in the area were lifted.
The FSA said there was "no evidence" of any offences under the Animal By-Products Regulations 2005.
In a statement, the FSA said: "We have carefully scrutinised and considered the evidence in this case and concluded there is insufficient evidence to provide a realistic prospect of conviction.
"Accordingly, we have decided not to proceed to a prosecution in this case."
The watchdog said its decision followed a thorough examination into possible problems with food waste storage at the plant.
Meanwhile, in a statement, Bernard Matthews said it has "always maintained that it has acted with the utmost integrity and cooperated fully with the relevant authorities".
The firm said "the Food Standards Agency's decision reinforces this".
The statement went on: "We have systems in place to ensure we meet and in some cases exceed the measures imposed by Defra, the FSA and the Meat Hygiene Service.
The FSA has been investigating Bernard Matthews on behalf of the Department for Environment, Food and Rural Affairs.
A spokeswoman for the government department said there are now no outstanding inquiries into the turkey firm which could lead to a prosecution.
Defra has said it expects its own scientific investigation into the bird flu outbreak to conclude after Easter.
The outbreak of the H5N1 flu strain at the Suffolk turkey plant prompted a cull of 159,000 birds.
An earlier Defra report, which was published in February, highlighted a number of failings at the turkey plant.
Inspectors saw gulls feeding on meat scraps which had been left in uncovered waste bins.
'Relief' and 'vindication'
And polythene bags used for meat products were left in open bins.
Liberal Democrat environment spokesman Chris Huhne has described the decision not to prosecute as "astonishing".
He said: "Given that the Defra-commissioned reports into the Bernard Matthews affair pointed clearly to breaches in the regulations, and that there was TV footage of wild birds feeding off open waste bins at the plant containing poultry meat, this is an astonishing decision."
He said he would ask ministers to provide a full explanation of the decision not to prosecute after Parliament returned from the Easter recess.
Miles Hubbard, of the T&G union, who represented the Bernard Matthews workers throughout the outbreak, expressed "a mixture of relief, vindication and confidence" at the result.
He said there was "relief that the prosecution 'cloud' has been blown away and vindication as the T&G always maintained that the standards of biosecurity at Holton were sound".