A mum has been left terrified after she discovered a stranger had been living in her roof for three weeks.

Monica Green, from Rockhamptom, Queensland, first figured something was amiss when she noticed things were out of place at her home.

While she was able to dismiss the concerns at first, when the mum-of-three arrived home from a doctor's appointment on Monday it was obvious things were askew.

The air conditioner was turned on and the back door was left open.

An even bigger tell-tale sign that something wasn't quite right came in the form of a half cooked meal of chicken nuggets, the Courier Mail  reports.

Ms Green immediately called the police who came round and found the attic door in the ceiling was askew.

It is thought a person was living in there for three weeks
It is thought a person was living in there for three weeks

“I felt like it was something out of a horror film,” she said.

“I’m meant to be the one that protects them (her children) and I feel like I’ve failed.”

Ms Green believes the person gained access to the house after stealing her keys.

She has since changed the locks.

"What has this person been doing in my house when I'm not home?" she told the New Zealand Herald.

"Were they trying to harm me or my kids? Did they want one of my kids?

Police discovered some had been living in the roof
Police discovered some had been living in the roof

"Were they going to come down at night and murder us?"

Before making the frightening discovery, Ms Green found her security camera system had been disabled.

Police discovered evidence of a person living in the attic, but they have not yet been found.

Jason Milner from Queensland Police said the incident was “certainly unique”.