The leaders of a youth brass band say they are left with "devastation" after their rehearsal space was broken into and "trashed" over the bank holiday weekend.
Camborne Youth Brass Band's musical director was alerted to the incident in Tuckingmill, Cornwall, by police at about 18:00 BST on Saturday.
A spokesperson for Devon and Cornwall Police said entry "was forced", with "considerable damage caused to the building's structure and contents – including a band's musical equipment".
Three 12-year-old girls and two 12-year-old boys were detained at the scene and inquiries were ongoing, police said.
Musical director Alan Pope told BBC Cornwall the amount of damage to equipment and memorabilia was "so upsetting," with "devastation everywhere".
He said equipment and music scores had been thrown from the stage, adding: "Then they put the fire extinguishers over everything, so everything was just soaking. Loads of equipment damaged, broken and smashed up."
Among the wreckage were banners from national championships, along with photos and trophies.
Pope said they were now working to clear up and repair the damage, including smashed glass and damage to the outside of the building.
He added the team was now also looking to arrange its own security "so that hopefully nothing like this will ever happen again".
An online crowd fundraiser with a target of £10,000 has been launched to help raise funds for repairs.
It had already reached just under £6,000 by 14:40 on Monday.
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Devastating Break-In Trashes Camborne Youth Brass Band’s Space