Published: 11:48, 15 May 2019
| Updated: 12:49, 15 May 2019
A dry ice machine set off a fire alarm at a school as teachers got ready for a story writing workshop.
Firefighters were called to pupils at St George's Primary School, Chequers Road, in Minster at about 8.45am today just before lessons started but stood down after it was found to be a false alarm.
Children were just arriving for the day and directed to the field while it was investigated.
In a letter to parents executive head teacher Howard Fisher said: "Our fire alarm first thing this morning was triggered by a dry ice machine that we were using in a classroom to help create the atmosphere for a story for writing.
"This is something we have done on at least a dozen occasions and has not triggered our alarms.
"Dry ice is not the same as smoke of course so should not trigger our alarms.
"However on this occasion it has and this resulted in an early evacuation before school started and of course the look of smoke coming out of the class.
"Thank you for your patience whilst you waited for us to ensure the pupils were safely accounted for."
He added that emergency crews had to struggle through traffic to get to the school.
Year Six pupils, who are currently sitting SATs exams, had extra play time before the tests.
Emergency crews had left by 9.04am.