CAMBRIDGE (CBS) – Thick, black smoke could be seen for miles above Cambridge Saturday afternoon as a large fire tore through a school.

The three-alarm fire broke out at the Martin Luther King Jr. and Putnam Avenue Upper schools around 2 p.m.

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“Both fire companies had extremely heavy fire conditions on the roof of the building,” said Cambridge Assistant Fire Chief Gerard Mahoney. “As is the case with most modern construction, it is a rubberized roofing. The rubber material, along with the cement that is used, it is extremely flammable.”

It appeared to be under control within an hour.

The school is under construction, the Cambridge Fire Department told WBZ-TV. Work crews were on scene at the time of the blaze but no one was hurt.

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Investigators do not know yet how the fire started.

Before the fire, the schools were supposed to be ready in September.
“We’ll have to see how that goes once we speak with all the contractors in the coming days,” said Cambridge Public Schools Superintendent Dr. Jeffrey Young. “Our aim is still to certainly try to get it open but the city is fantastic in managing these projects and I have a lot of confidence in the city manager.”

The fire did an estimated $2-to-$3 million in damage.

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The cause of the fire is under investigation.