MANTECA (CBS13) – Firefighters are working to extinguish flames in the attic of a building in Manteca.

Around 4:20 a.m. someone spotted smoke coming from two-story the building on the corner of Sycamore and West Yosemite avenues and called 911. The structure was on fire when firefighters arrived.

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Crews are not being allowed to enter the building because they believe the second floor was compromised and could collapse.

Firefighters have cut holes in the roof of the building to continue their attack.

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Although the building has been boarded up for the last 18 months, firefighters do not think squatters were living inside at the time. The cause of the fire is under investigation.

Personnel from Tracy, Ripon and Lathop fire departments were on the scene to assist Manteca crews.

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Residents are being asked to avoid the area.