ARSONISTS were warned they could be trapped in a derelict Blackburn school after it was torched for the third time in five months.

Three fire crews were called to the old St Wilfrid's C of E High School and Technology College site, in Byrom Street, at 11.15pm yesterday to battle the flames for 30 minutes.

Today, the buildings' owners revealed they have been trying to sell them to give the area a new lease of life.

Police and firefighters launched a joint investigation into the blaze, which destroyed more than eight square metres. The fire is being treated as deliberate.

The building, which is still owned by the Blackburn Diocese, was targeted twice in April and both fires were started in cupboards under stairs. Station officer Aidan Fortune said: "There was evidence that the building had been broken in to.

"We used the aerial platform and four jets to fight the fire and checked the annexe to make sure there were no other seats.

"People breaking in to the building need to be very aware that they are very trapped and should leave well alone."

The caretaker was also called to the scene last night and told fire crews it had been last checked on Wednesday and had been secure.

Inspector Stuart Bruce said: "A derelict building in the centre of town is always going to be a problem with vandals. We are conducting a joint investigation as to how the fire started."

A spokesperson for the Diocese added: "We are currently in talks with possible purchasers for the site.

"At present there is a caretaker looking after it and making visits two to three times a week to ensure it remains secure."