BILLERICA (CBS) – Firefighters in Billerica had to contend with massive piles of what officials described as “clutter” blocking their way as they battled flames inside a home that caught fire on Saturday morning.

The fire, at 12 Autumn Street, is believed to have started in the basement sometime around 7:45 a.m.

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Officials say firefighters first attempted to go into the house through the front door, but the entrance was blocked.

They eventually managed to get into the home through a rear door.

The homeowner, an elderly female, escaped the fire safely.

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There were three cats inside the house, two of which died. The third cat is missing.

Officials say a responding firefighter was injured when he fell down a flight of stairs. Officials blamed the fall on the excessive clutter.

The cause of the fire is under investigation.

The Board of Health has also been called in to work with fire inspectors.

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