INVESTIGATORS were last night trying to establish the cause of a fire that tore through a school science lab.

Pupils at De La Salle high, in Croxteth, were evacuated when the blaze broke out in the second-floor classroom.

Reports initially suggested that a laboratory experiment had gone wrong, though fire chiefs said that the room had been locked and unoccupied.

The classroom was “well alight” when firefighters arrived on scene at 12.55pm yesterday. Three crews tackled the blaze for just over an hour.

Investigators were on site trying to establish the cause of the fire, which gutted the classroom and damaged a corridor and adjoining classroom.

Watch manager Tony Lynott said the flames could easily have spread, had it not been for a quick response.

He said it was likely an electrical fault was responsible for the blaze.

Mr Lynott said: “When we arrived, the classroom was well alight and the door was locked so we had to break in.

“The classroom was quite large, about 15m, and it was gutted, but thankfully we kept the smoke damage elsewhere to a minimum.”