Pupils at a Blackpool primary school were told not to come in after a break-in caused a fault with the building’s alarm.
Children at St John’s Church of England Primary School, on Church Street, were given the day off as engineers struggled to switch off the building’s fire alarm, which had been sounding all night.
It is believed the problem was caused during a break-in at around 6.55pm on Monday.
Police said an intruder had climbed a rear wall before using scaffolding, which is part of an ongoing extension, to gain access through an open window.
Gill Hicks, school business manager, said: “The children have obviously missed a day and people are a bit upset.
“We know the children were quite upset – they do value the school – but we are fine.
“There was no substantial damage but it’s still quite upsetting and inconvenient for parents to be told at very short notice the school will be closed.
“We don’t like closing but there was no alternative – the alarm was extremely loud.”
The school, which has around 200 pupils, said the alarm took most of the morning to deactivate. Lessons will go ahead as normal on Wednesday.
A Lancashire Police spokesman said: “They (the burglars) have activated the fire alarm while inside.
“It is not clear how many people were involved.”
Police have issued a description of a man seen in the area at the time of the incident.
He is described as white, in his mid to late 20s, of heavy build and wearing a black hoodie with white shorts and carrying a black rucksack.
Anyone with information about the incident is asked to call police on 101, quoting log number 1266 of September 29.