A classroom at the Mount Barker Waldorf School in the Adelaide Hills has been destroyed by a suspicious fire on Tuesday morning.

Emergency services raced to the scene about 4am, with both MFC and CFS crews responding to a fire at the Waldorf School on Sims Rd.

Four people and a dog were were safely evacuated from the scene, with no reports of injuries.

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Those present were there on a school camp.

The MFS issued a smoke warning for Hills residents, with thick black clouds coming from the southwest direction of the Sims Rd area - this advice has since been rescinded.

SAPOL have called the fire suspicious, and urges anyone with information to contact police.

Fire investigators are working to determine the cause.

It comes only a day after a suspicious fire at another private college in South Australia.

Emergency teams responded to reports that a building was on fire at St Mark’s College at Port Pirie South, just after 3.30am on Monday.

Two 15-year-old boys from Port Pirie have since been charged with arson.

Nobody was injured in the blaze.