A town centre street in Limavady will remain closed into Friday after asbestos was found at the site of a large fire.
The blaze broke out at a derelict former nightclub on Catherine Street just after 17:40 BST on Thursday.
More than 50 firefighters were at the scene during the height of the blaze.
The fire was brought under control on Thursday evening, with one fire crew remaining at the site in the early hours of Friday.
A senior firefighter said Catherine Street was quickly evacuated but it will stay closed due to the discovery of asbestos.
David Doherty, western area commander for the Northern Ireland Fire and Rescue Service (NIFRS), said the quick response of firefighters stopped the blaze from spreading further.
“Luckily we were able to resource this fire very, very quickly and we were able to stop it spreading up and down the terraced area,” he said.
“That was the fear, that this would spread to adjoining businesses. Now, there has been some damage caused to those adjoining businesses but because we were able to get appliances here quickly we were able to mitigate that as much as we could.”
Causeway Coast and Glens council have been informed of the asbestos, Cdr Doherty said, and are arranging for specialist contractors to attend the scene.
The cause of the fire is not yet known. An investigation will begin on Friday.
The Police Service of Northern Ireland (PSNI) said a number of diversions around Catherine Street are in place.