Demolition work on a nuclear clean-up site in Cheshire has been brought to a halt because of roosting bats.
The bats may delay demolition work for months
Delays of up to four months are predicted at the former uranium enrichment facility at Capenhurst after a colony of pipistrelle bats was found.
The bats have been hibernating over the winter but in recent weeks they have woken up and may start breeding.
A British Nuclear Group spokesman said they were working with environmental experts to protect the animals.
Ian Thomas, of British Nuclear Group, said: "During this project we became aware that we had a colony of bats roosting in the structures that were earmarked for demolition.
The pipistrelle is the smallest bat in the UK
"Given the protected status of bats, we took immediate action to prevent any further disturbance of the colony by stopping all demolition works and hiring a local ecological consultant to determine the best course of action to protect the bat colony.
Pipistrelles are the smallest and commonest bat in the UK and can live for up to 16 years.
They usually hibernate from mid-November to the beginning of April and weigh about eight grammes.