A secondary school had to be evacuated for the third time in three days after a newly-installed fire alarm went off again.

The latest incident at Walderslade Girls School happened at about 10am on Friday when the ultra-sensitive system was triggered.

Once it was established there was no fire, pupils were allowed back to class within five minutes.

An investigation after the first alarm sounded on Tuesday revealed it had been sparked by deodorants.

Head teacher Louise McGowan has since sent a text message to parents banning aerosols from being brought on to the site in Bradfields Avenue.

Deputy head Dr Fraser Campbell said staff were looking into what caused Friday’s incident and a similar one on Thursday morning.

Dr Campbell, said: “We knew there were going to be teething problems There are about 100 heat and smoke sensors around the school. What we need to do now is to educate staff and children to act responsibly.”

Mrs McGowan, said earlier: “We thought it would be things like burning a piece of toast, but as it was a hot day, a lot of the girls got their deodorant out after they had PE and ended up setting off.”

She added that if students wished to bring a deodorant to school it must be a roll-on.

One parent, who did not wish to be named, was anxious after receiving the text from Mrs McGowan saying there had been “a serious incident” at the school.

She said: “I feared the worst.”