UPDATE, 2:06 p.m.: Nobody was hurt in the fire, according to the Waltham Police Twitter feed. Officers were the first to arrive on the scene and helped clear the building, according to police. 

Also, firefighters removed two charred mattresses from the home. 

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UPDATE, 1:13 p.m.: The fire has been knocked down and crews are overhauling the building.

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Waltham firefighters are responding to a report of a fire at 11 Spruce St., according to Twitter and scanner reports. 

The fire has reportedly been contained to a mattress and did not make it into the walls, according to scanner traffic. Firefighters are checking the residence, according to scanner traffic. The building is a 2.5 story woodframe structure, according to Twitter traffic.  

Stay tuned to Waltham Patch for updates.