People exploring derelict buildings are endangering lives and should think of the consequences before entering.
This Lancashire Fire and Rescue Service warning comes following the major blaze at the former Ivy Bank High School on Sunday afternoon.
Crews spent two hours tackling the fire which had engulfed the top floor of the four-storey Byron Street building and sent black plumes of smoke billowing across the town.
Lancashire Fire and Rescue Service spokesman, John Taylor, said it was imperative that people heeded their warning and stayed clear of such buildings.
"Derelict buildings like Ivy Bank, they do present a hazard," he said. "There can be roof or structural issues, unsafe floors and stairs. And these can vary in severity depending on how long they have been left. It is clearly a hazardous environment and we do advocate staying away from such buildings.
"There are groups you see on social media called 'urban explorers' who explore these derelict buildings taking photos or recording film and we ask these people not to follow that particular hobby.
"When firefighters approach a building like this, they take steps to stay safe. If it is judged to be unsafe then they will attempt to extinguish the fire from outside the building but obviously if it is apparent that there is somebody in the building they will commit to going inside."
An investigation is under way into how the Ivy Bank blaze started and Mr Taylor said: "The investigation is ongoing. Buildings like this do not tend to spontaneously set alight and so the there is a possibility of arson. Derelict building like this are obviously a target for arsonists.
"Again, we would implore people to stay clear of buildings like this and we would ask anybody who sees anything suspicious to report it to the authorities."
The Ivy Bank building has been derelict since the school closed in 2006 when it merged with Habergham High School to form Hameldon Community College.
It was due to be bulldozed to make way for a mixture of detached and semi-detached homes.
Mr Taylor said it was frustrating that buildings of this size could languish in communities for years but understood selling them is a lengthy process.
"It is difficult because with buildings like Ivy Bank there is a lot of negotiating that goes on between the council and potential developers.
"This can take a long time and it means that they can end up languishing within a community for a number of years and become an eyesore for everybody. Nobody wants this."
Anybody with an information on the Ivy Bank blaze can ring police on 101 or Crimestoppers, anonymously, on 0800 555 111.